Laser Irradiation Device, Laser Irradiation System, and Method for Removing Coating or Adhering Matter

ABSTRACT

In order to provide a laser irradiation system, a method for removing a coating, and a laser irradiation apparatus capable of efficiently removing a coating on a surface of a structure and recovering the removed substance using suction, a laser head ( 3 ) is configured from an optical system ( 4 ) for irradiating laser beam ( 30 ), a suctioning means ( 33 ) for suctioning removed matter ( 60 ) produced at the point where the laser beam ( 30 ) is directed, and an attachment ( 5 ) configured to be capable of abutting a surface ( 20 ) of a structure, the optical system ( 4 ) being operated to scan the irradiation point of the laser beam so as to draw a trajectory of a circle having a radius r 1  around the optical axis of the laser beam ( 30 ) on a surface substantially perpendicular to the optical axis.

TECHNICAL FIELD

The present invention relates to a technology for removing a coating ona surface of a structure by laser irradiation and forsuctioning/collecting the removed matter and particularly to a laserirradiation apparatus for removing the coating or the adhering matter byirradiating a laser beam using a portable laser head to a fixed or largestructure such as a bridge, a building, a boat, a pipeline and the likeas a structure, a laser irradiation system, and a method for removing acoating or adhering matter using such apparatus and system.

BACKGROUND ART

In order to use the structures safely for a long time which aredifficult to be moved such as a bridge, an express way, an elevatedtrack for a railway, a building, a tank, a machine facility and thelike, a coating of painting applied on a surface of a base material(steel material) needs to be periodically peeled off, removed, andre-painted in order to prevent corrosion. As a prior-art method forremoving a coating, there were a method by blast treatment such assandblast for removing a coating by blowing sand, a method of using acoating remover, and a method of using a mechanical tool. In the methodby blast treatment, a large quantity of secondary waste is generated.This secondary waste is a mixture of a powder dust of a coatingcontaining harmful matters such as lead, chromium hexavalent, PCB andthe like and an abrasive material such as silica sand, garnet and thelike, which gives a large load to the environment and requires a largetreatment cost. Moreover, since the abrasive material is blown bycompressed air, there is a concern that even the base material under acoating layer is damaged. Moreover, there is also a problem of a largenoise caused at collision of the abrasive material. The methods of usinga coating remover and the mechanical tool, they both have a problem thata treatment area per time is small, which is not efficient, and each hasproblems that a waste of the agents is generated and the noise is large.

Patent Literature 1 discloses a method of removing a coating by a lasertreatment apparatus in order to improve working efficiency and to avoida risk against the prior coating removal of an outer plate of such as anaircraft fuselage by blowing a highly toxic drug to the coating surfaceand scraping off the coating film by a manual work. The laser treatmentapparatus described in Patent Literature 1 includes a lens forirradiating a laser beam to a surface of a treatment target, a lenssupporting mechanism which supports the lens and can adjust a heightfrom the treatment target surface to the lens, and a gas injecting meansfor blowing gas to a laser irradiation portion. Moreover, it isdescribed that a gas inlet arranged in a box-shaped vessel exhausts thegas in the box-shaped vessel and exhausts the removed matter scatteredfrom the laser irradiation portion. It is also described that a sweepingprocess for sweeping an irradiation position of the laser beam to afirst direction by using a first deflector arranged in an optical pathof the laser beam incident to the lens and moving the irradiationposition of the laser beam in the first direction within the surface ofthe treatment target by changing a traveling direction of the laser beamand a second deflector arranged in the optical path of the laser beamincident to the lens and moving the irradiation position of the laserbeam in a second direction crossing the first direction within thesurface of the treatment target by changing the traveling direction ofthe laser beam is performed a plurality of times while shifting in thesecond direction crossing the first direction. It is described that, insuch a laser treatment apparatus, a laser irradiation head is mounted ona tip-end of a manipulator arm, and the manipulator arm is controlled bya manipulator body and moves and supports the laser irradiation head toa desired position on the surface of the treatment target.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Laid-Open No. 10-309899

SUMMARY OF INVENTION Technical Problem

According to the technology described in Patent Literature 1, thecoating film on the surface of the treatment target can be removed bylaser abrasion without using chemical products, and the removed matterscattered from the surface of the treatment target can be collected andexhausted by using a gas suctioning means.

However, since the laser irradiation head described in Patent Literature1 is supported by the manipulator arm and moved to the desired position,it is difficult to be used in an environment in which a sufficient workspace cannot be ensured or for a structure having a complicated shape.Moreover, it is also difficult to be carried and handled by a worker. Tobegin with, the laser treatment apparatus described in Patent Literature1 is a laser treatment apparatus to be applied to coating removal ofsuch as an aircraft stored in a plant and the like, and movement of suchlaser treatment apparatus itself is not considered. That is, the coatingThe laser irradiation apparatus according tore 1 cannot be applied tocoating removal of a structure that cannot be moved easily (such as abridge, and an expressway, an elevated track for a railway, a buildingand the like, for example).

Moreover, in Patent Literature 1, the first deflector such as a galvanomirror, a polygon mirror and the like for a scanning optical system isused so as to linearly scan the irradiation position of the laser beam(hereinafter referred to as linear scanning). With the method ofrepeating such linear scanning, it is difficult to efficiently treat awide range in a short time, and the surface of a wide range of astructure such as a bridge cannot be treated with a low cost. Moreover,in the linear scanning with the laser beam, since its optical pathlength is changed and a relative distance between a focal point of thelaser beam and an actual irradiation point is changed, uniform coatingremoval could not be performed. Note that a complicated mechanism isrequired for control of the focal point of the laser beam in accordancewith the change in the optical path length by linear scanning with thelaser beam. Moreover, if return light of reflection of the laser beamirradiated to the coating surface enters into the laser mechanism, thereis a possibility that a fiber or the like is damaged. A complicatedmechanism is usually needed in order to prevent damage by the returnlight, but it is difficult to provide such a mechanism in a portablesmall-sized laser head. Furthermore, in Patent Literature 1, the removedmatter scattered from the surface of the treatment target is collectedby the suctioning means, but there is a concern that a part of theremoved matter generated from the laser irradiation point adheres to thescanning optical system, and in this case, not only that energy of thelaser beam is damped but also, a temperature of the adhesion spot israised by the laser beam, and the optical system might be broken.

The present invention has an object to provide a laser irradiationapparatus and a laser irradiation system including a small-sized andlight-weighted laser head that can solve at least a part of theabove-described problems.

Solution to the Problems

In order to solve the above-described problems, a laser irradiationapparatus of the present invention includes a laser oscillator, a fiberfor transmitting a laser beam outputted from the laser oscillator, and aportable laser head for focusing the laser beam transmitted via thefiber and irradiating it to a surface of a structure, in which the laserhead includes an optical system for irradiating the laser beam and ashielding member for protecting the optical system from a removed mattergenerated from an irradiation point of the laser beam, and the opticalsystem scans the irradiation point of the laser beam on a surfacesubstantially perpendicular to an optical axis of the laser beam so asto draw a trajectory of a circle having a radius r around the opticalaxis.

In the laser irradiation apparatus, it is preferable that the opticalsystem has a first wedge prism for deflecting the laser beam to adirection going outward from the optical axis, a second wedge prism fordeflecting the laser beam deflected by the first wedge prism to adirection of the optical axis, and a driving means for rotating thefirst wedge prism and the second wedge prism together around the opticalaxis, and the shielding member is mounted on a tip-end of the laser headand has an emitting port through which the laser beam is passed on theoptical axis. Moreover, a suction source and a suctioning means forsuctioning a removed matter generated from the irradiation point of thelaser beam may be provided. The laser head may include an attachmentconfigured to be capable of abutting on the surface of the structure.

A laser irradiation apparatus of the present invention includes a laseroscillator, a fiber for transmitting a laser beam outputted from thelaser oscillator, a suction source and a portable laser head forfocusing the laser beam transmitted via the fiber and irradiating it toa surface of a structure, in which the laser head includes an opticalsystem for irradiating the laser beam, a suctioning means for suctioninga removed matter generated from the irradiation point of the laser beamand an attachment configured to be capable of abutting on the surface ofthe structure, and the optical system is configured to scan theirradiation point of the laser beam on a surface substantiallyperpendicular to an optical axis of the laser beam so as to draw atrajectory of a circle having a radius r around the optical axis.

In the laser irradiation apparatus, the attachment is preferablyconfigured such that the surface of the structure is arranged at adistance equal to or closer than a focal distance of the laser beam whenabutting on the surface of the structure. Moreover, it is preferablethat the optical system has a variable focusing mechanism, the laserhead has a distance sensor for measuring an inter-surface distance froma principal point of the optical system to the surface of the structure,and a control unit for changing the focal distance of the laser beam bythe variable focusing mechanism of the optical system so as to be thesame as the inter-surface distance measured by the distance sensor orlonger than that is provided. Moreover, the surface of the structure ispreferably arranged within a range of −5 to −25 mm closer to the laserhead side than the focal point of the laser beam.

In the laser irradiation apparatus, it is preferable that the laser headhas a sensor for detecting abutting or approaching of the attachment tothe surface, and a control unit for limiting irradiation of the laserbeam is provided if abutting or approaching of the attachment to thesurface is not detected by the sensor. Moreover, it is preferable thatthe laser head has a vibration sensor for detecting vibration and avibrating means, and a control unit for vibrating the laser head by thevibrating means if vibration detected by the vibration sensor is smallerthan a predetermined threshold value is provided.

In the above-described laser irradiation apparatus, the optical systempreferably has a first wedge prism for deflecting the laser beam withrespect to the optical axis, and a driving means for rotating the firstwedge prism and a shielding member arranged between the first wedgeprism and the surface of the structure around the optical axis.Moreover, the optical system preferably has a deflecting means forfurther deflecting the laser beam deflected by the first wedge prismwith respect to its optical path and scans, on a circumference of thefirst circle on the surface substantially perpendicular to the opticalaxis, an irradiation point of the laser beam so as to draw a trajectoryof a second circle having a radius r2 around a moving point. It ispreferable that a deflection angle of the deflecting means is smallerthan a deflection angle of the first wedge prism.

It is preferable that the deflecting means is the second wedge prism,the first wedge prism rotates at a first rotation speed, and the secondwedge prism rotates at a second rotation speed faster than the firstrotation speed. Moreover, the attachment preferably has a mirror forreflecting the irradiated laser beam to a side surface of a protrusionformed on the surface of the structure.

Moreover, the laser irradiation apparatus preferably includes a distancesensor for measuring an inter-surface distance from a principal point ofthe optical system to the surface of the structure and a control unitfor changing a focal distance of the laser beam by a variable focusingmechanism of the optical system so that the focal distance becomes equalto or longer than the inter-surface distance measured by the distancesensor. The attachment preferably has an expansion/contraction mechanismcapable of changing the inter-surface distance from the principal pointof the optical system to the surface of the structure. It is preferablethat the laser head has a sensor for detecting that the attachment is incontact with or approaching to the surface, and a control unit forcontrolling irradiation of the laser beam is provided if contact orapproach of the attachment to the surface is not detected by the sensor.

In the laser irradiation apparatus, the laser head may be configured tohave a moving means for traveling inside a pipeline, and to cause theoptical system to scan an irradiation point of the laser beam so as todraw a trajectory of a circle having a radius r corresponding to ½ of aninner diameter of the pipeline. The optical system may have a reflectivemirror for reflecting the laser beam at a predetermined angle and adriving means for rotating the reflective mirror around an optical axisso that the irradiation point of the laser beam is scanned in the rearof a tip-end of the laser head. It is preferable that the optical systemhas a replaceable optical unit including an optical member for focusingor deflecting the laser beam and a body portion including a drivingmeans for rotating the replaceable optical unit, and the replaceableoptical unit is configured to be detachable to the body portion. Thelaser head preferably has at least two irradiation means for irradiatinga red laser beam, each of the irradiation means is arranged so that thered laser beam is irradiated diagonally to the optical axis of theoptical system and the red laser beams irradiated from the at least twoirradiating means cross each other at a predetermined position.

In any one of the above-described laser irradiation apparatuses, thelaser head preferably has a gas blowing means for blowing a gas suppliedfrom a gas supply source in the vicinity of the irradiation point of thelaser beam. The gas blowing means preferably fills the inside of ahousing with a gas flow. The laser head preferably has an auxiliaryirradiation means for applying energy to the vicinity of the irradiationpoint of the laser beam. Moreover, the laser head preferably has acooling means for cooling at least a part of the optical system. In theoptical system, a fiber connection portion connected to a tip-end of thefiber preferably has a lens for focusing the laser beam. It ispreferable that energy density per unit time at a focal point of thelaser beam is within a range of 1.25×10⁻⁴ to 5×10⁻⁴ J/μm², and a spotdiameter of the irradiation point is within a diameter range of 20 to200 μm. It is preferable that a control unit for stopping irradiation ofthe laser beam of the laser head is provided if it is determined by thesensor group provided on the laser head that the laser beam is deviatedfrom the desired position. It is preferable that the laser head has asurface state detection sensor for detecting a state of the surface or acamera for observing a state of the surface, and a display apparatus fordisplaying information relating to the state of the surface obtained atleast either one of the surface state detection sensor and the camera isprovided. A control unit for setting a laser irradiation condition onthe basis of the information relating to the state of the surface ispreferably provided.

Moreover, the laser irradiation apparatus preferably includes acommunication function connectable to a network and a control unit fortransmitting the information to a server via the network using thecommunication function, obtaining the laser irradiation conditionselected in the server, and setting the irradiation condition of thelaser. The laser oscillator is preferably of a continuous oscillationtype. The laser oscillator preferably generates a laser beam having anoutput within a range of 200 to 500 W and a wavelength within a range of1060 to 1100 nm.

Any one of the above-described laser irradiation apparatuses ispreferably mounted on a vehicle configured to be movable.

A laser irradiation system of the present invention includes: a laserirradiation apparatus including a laser head provided with a surfacestate detection sensor for detecting a state of a surface of a structureand a communication function connectable to a network; and a serverconnectable to the network, and is characterized in that the serveracquires information relating to the state of the surface detected bythe surface state detection sensor by the communication function via thenetwork from the laser irradiation apparatus and selects a laserirradiation condition on the basis of the information relating to thestate of the surface of the structure, and the laser irradiationapparatus acquires the selected laser irradiation condition and iscapable of laser irradiation on the basis of the selected laserirradiation condition.

In the above-described laser irradiation system, the laser irradiationapparatus is preferably mounted on a vehicle configured to be movable.The laser irradiation apparatus preferably has a control unit limitingirradiation of a laser beam until an irradiation allowing signal isacquired from the server. If it is determined by the sensor groupprovided on the laser head that the laser beam is deviated from thedesired position, the server preferably stops irradiation of the laserbeam of the laser head. The server preferably acquires informationrelating to a state of the surface of the structure after laserirradiation detected by the surface state detection sensor by thecommunication function via the network from the laser irradiationapparatus and makes it into a database by associating it with theselected laser irradiation condition. Moreover, the server preferablyacquires information relating to maintenance and management of the laserirradiation apparatus including a use state of the laser irradiationapparatus and maintains and manages the laser irradiation apparatus.

An aspect of the present invention includes a vehicle characterized bymounting any one of the above-described laser irradiation apparatuses.

A server of the present invention is characterized by selecting a laserirradiation condition on the basis of information relating to a state ofa surface acquired by a surface state detection sensor via a networkfrom a laser irradiation apparatus including a laser head provided withthe surface state detection sensor for detecting the state of thesurface of the structure and a communication function connectable to thenetwork, and then transmitting the selected laser irradiation conditionto the laser irradiation apparatus.

In the above-described server, it is preferable to transmit anirradiation allowing signal for allowing irradiation of the laser beamto the laser irradiation apparatus.

A coating removing method of the present invention is a method forremoving a coating of a surface of a structure by laser irradiation andis characterized in that a laser irradiation apparatus including a laseroscillator, a fiber for transmitting a laser beam outputted from thelaser oscillator, a suction source and a portable laser head forfocusing the laser beam transmitted via the fiber and irradiating it tothe surface of the structure is moved to an installation place of thestructure, and the laser head irradiates the laser beam transmitted viathe fiber on a surface substantially perpendicular to an optical axis ofthe laser beam so as to draw a trajectory of a first circle having aradius r1, while a removed matter generated from the irradiation pointof the laser beam is suctioned.

A coating removing method of the present invention is a method forremoving a coating of a surface of a structure by laser irradiation andis characterized in that a laser irradiation apparatus including a laseroscillator, a fiber for transmitting a laser beam outputted from thelaser oscillator, a suction source and a portable laser head forfocusing the laser beam transmitted via the fiber and irradiating it tothe surface of the structure is moved to an installation place of thestructure, and the laser head irradiates the laser beam transmitted viathe fiber on the surface so that an inter-surface distance from aprincipal point of the optical system to the surface of the structure isequal or shorter than a focal distance of the laser beam, while aremoved matter generated from the irradiation point of the laser beam issuctioned.

In the above-described coating removing method, the surface of thestructure is preferably within a range of −5 to −25 mm closer to thelaser head side than the focal point of the laser beam.

A method for removing an adhering matter of the present invention is amethod for removing an adhering matter inside a pipeline by laserirradiation and is characterized in that a laser irradiation apparatusincluding a laser oscillator, a fiber for transmitting a laser beamoutputted from the laser oscillator, a suction source and a laser headplaced on a moving means capable of traveling inside the pipeline andirradiating the laser beam transmitted via the fiber is moved to aninstallation place of the pipeline, the laser head is made to travelinside the pipeline while an irradiation point of the laser beam isscanned so as to draw a trajectory of a circle having a radius rcorresponding to ½ of an inner diameter of the pipeline, and a removedmatter generated from the irradiation point of the laser beam issuctioned. In any one of the above-described methods, an irradiationcondition of the laser beam may be changed in the laser head by removinga replaceable optical unit including an optical member for focusing ordeflecting the laser beam from a body portion and by mounting anotherreplaceable optical unit on the body portion.

Advantageous Effect of Invention

According to the present invention, by using a transportable and movablelaser irradiation apparatus including a small-sized and light-weightedlaser head, in a site of a structure that cannot be moved easily, acoating on the surface or the like can be removed and the removed mattercan be suctioned and collected. Moreover, by a laser head provided withan optical system capable of circular scanning, the surface in a widerange can be efficiently treated, and a cost for removing a coating canbe reduced. The other effects will be described in an embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an outline configuration diagram of a laser irradiationapparatus of the first embodiment.

FIG. 2A is an explanatory view illustrating a positional relationshipbetween a focal point and an irradiation point.

FIG. 2B is a diagram for roughly explaining a positional relationshipbetween a focal point and an irradiation point when a laser beam isdeflected.

FIG. 3 is an outline configuration diagram of a laser head of the secondembodiment.

FIG. 4 is an explanatory diagram illustrating a trajectory of a laserirradiation point of the second embodiment.

FIG. 5 is an outline configuration diagram of a laser head of the thirdembodiment.

FIG. 6 is an explanatory diagram illustrating an example of a trajectoryof a laser irradiation point according to the third embodiment.

FIG. 7 is an explanatory diagram illustrating another example of thetrajectory of the laser irradiation point of the third embodiment.

FIG. 8 is an explanatory diagram illustrating an attachment of a laserhead of a fourth embodiment.

FIG. 9 is an explanatory diagram illustrating another example of theattachment of the fourth embodiment.

FIG. 10 is an explanatory diagram illustrating still another example ofthe attachment of the laser head of the fourth embodiment.

FIG. 11 is an outline configuration diagram of a laser head of a fifthembodiment.

FIG. 12 is an example of a distance measurement means of the laser headof the fifth embodiment.

FIG. 13 is an example of a focal point by the distance measurement meansof the laser head of the fifth embodiment.

FIG. 14 is an outline diagram illustrating a laser irradiation system ofa sixth embodiment.

FIG. 15 is an outline configuration diagram illustrating an example of alaser head of a seventh embodiment.

FIG. 16 is an outline configuration diagram illustrating another exampleof the laser head of the seventh embodiment.

FIG. 17 is an outline configuration diagram illustrating an example of alaser head of an eighth embodiment.

FIG. 18 is an outline configuration diagram illustrating another exampleof the laser head of the eighth embodiment.

FIG. 19 are outline configuration diagrams illustrating a scanningoptical system including a replaceable optical unit of a ninthembodiment

FIG. 20 are outline views of an example of the laser head of the presentinvention.

EMBODIMENTS OF INVENTION

The present invention is a laser irradiation apparatus and a laserirradiation system including a small-sized and light-weighted laser headfor efficiently removing a coating formed on a surface of a structure ina short time and configured transportable and movable to a work site.Moreover, a method for removing a coating using such a laser irradiationapparatus and laser irradiation system is included. Here, the structureincludes those fixed to an installation place and cannot be easily movedsuch as a bridge, an expressway, an elevated track of a railway, alarge-sized tank, a large-sized facility and the like and also includesthose that can be moved to a service place such as an aircraft, a boat,a railway vehicle and the like. Furthermore, the structure includes apipeline installed in various facilities.

The present invention is mainly intended to remove a coating on thesurfaces of these structures but can be also applied to treatment onsurface alteration such as undercoat treatment in overhaul inspectionsof a large-sized tank, pre-welding treatment of a large-sized mechanicalfacilities and the like and removal of stains or rusts of port andharbor facilities. Moreover, stains, graffiti and the like adhering to aconcrete surface can be also removed. Furthermore, adhering matters,deposited matters, stains, rusts and the like adhering to the surfaceinside the pipeline (hereinafter collectively referred to as adheringmatters) can be also removed. Particularly, it is preferably used forremoval of radioactive-contaminated paint, adhering matters and thelike.

The laser irradiation apparatus of the present invention includes atleast a laser head, a laser oscillator, and a fiber for transmitting alaser beam outputted from the laser oscillator. The laser head isconnected to the laser oscillator via the fiber and has an opticalsystem for scanning an irradiation point of the laser beam. Note that,depending on the case, if a removed matter generated from the laserirradiation point is scattered and enters into the laser head andadheres to the optical system (lens), there is a concern that atemperature of the adhesion spot becomes high and the optical system isbroken. Thus, a shielding member for protecting the optical system fromthe removed matter generated from the laser irradiation point ispreferably provided in the laser head.

It is only necessary that the shielding member can prevent adhesion ofthe removed matter to the optical system inside the laser head, and itsshape and arrangement can be set as appropriate in accordance with amode of irradiation of the laser beam, a configuration of the laser headand the like. The shielding member is preferably arranged between anemitting end surface of the optical system and a surface to be treated.The shielding member may have a cylindrical shape covering an opticalpath of the laser beam (see FIG. 3) or may have a dome shape (see FIG.16). Moreover, it may have a plate shape covering an emitting port of ahousing 32 (see FIG. 10). If the optical system is configured to berotatable around an optical axis as will be described later, theshielding member may be provided so as to rotate with the optical systemor may be provided independently from rotation of the optical system.The laser irradiation apparatus of the present invention may use a laserbeam having a conical shape flared to the end and in this case, theemitting port can be made wider so that a rotating laser beam can passthrough or the shielding member may be rotated in accordance with arotation speed of the laser beam (see FIG. 3). In a configuration inwhich one emitting port of the shielding member is provided on theoptical axis and the flared conical laser beam is deflected toward theemitting port of the shielding member, the flared conical laser beam canbe irradiated from a small emitting port without rotating the shieldingmember, which is particularly preferable (see FIG. 15). Note that theemitting port through which the laser beam is to be passed in theshielding member may be constituted as a physical opening or may beconfigured by a light-transmittable member which can transmit the laserbeam instead of the physical opening. The entire shielding member may beconstituted by a light-transmittable member, and in this case, theemitting port of the laser beam can be an appropriate position.Moreover, it is preferable that the shielding member is provideddetachably so that it can be replaced when being stained.

If the removed matter generated from the laser irradiation point is notto be scattered to a periphery from the viewpoint of environmentalpreservation, the laser irradiation apparatus of the present inventionmay be provided with a suction source as necessary or may be providedwith a suctioning means for suctioning the removed matter in the laserhead. If the suctioning means is provided in the laser head, most of theremoved matter generated at the laser irradiation point is collected bythe suctioning means, but the removed matter might be drawn to anemitting end of the optical system, and there is concern that a part ofthe removed matter generated at the laser irradiation point adheres tothe optical system. Thus, when the suctioning means is provided in thelaser head, a shielding member for protecting the optical system fromthe removed matter generated at the laser irradiation point ispreferably provided as necessary.

Moreover, the laser head may be attached with an attachment on a tip-endthereof and can move while being in contact with the surface of thestructure. The attachment is preferably constituted detachably.

The laser head is preferably portable so that a worker can work on itmanually. Alternatively, the laser head may be placed on a moving means(a conveying means). It is only necessary that the moving means iscapable of relatively moving the laser head with respect to a surface tobe treated and is not particularly limited. For example, it may be soconfigured that a manipulator is used as the moving means and the laserhead is moved as appropriate along the surface of the structure.Moreover, a self-propelled or manually movable carriage and the like maybe used as the moving means. In this case, the laser head can travelinside the pipeline, for example. In addition to the carriage on whichthe laser head is placed, the self-propelled moving means includes adriving means (a motor, an engine, an actuator and the like), adriving-force transmitting means for transmitting a driving force fromthe driving means to an internal wall of the pipeline and the like (aroller, a tire, a caterpillar and the like), a remote control means(including a wireless or wired communication unit, a control unit of thedriving means and the like) and the like. When the manual moving meansis to be constituted, it may be so configured that a wire or a rod orthe like is connected to the carriage on which the laser head is placedso that the laser head is moved by operation of the worker. When thelaser head is to be travelled by itself or manually inside the pipeline,the carriage on which the laser head is placed preferably has acylindrical shape conforming to an inner diameter of the pipeline (seeFIGS. 17 and 18).

In the method for removing a coating using this laser irradiationapparatus, the surface to be treated is preferably arranged at the focaldistance of the laser beam or in front of the focal distance and isparticularly arranged so that, assuming the focal point is a reference(0), the laser head side (near distance) is negative, and the depth side(far distance) is positive, the surface to be treated is located withina range of preferably 0 to −30 mm or more preferably of −5 to −25 mm.

Energy is concentrated the most at the focal point of the laser beam,but a treatment region (spot diameter) becomes narrow to the contraryand thus, treatment capability of coating removal deteriorates. Sinceenergy is too strong depending on the case, an undercoat might bedamaged or ignited. Thus, the treatment region (spot diameter) can bemade wider so that treatment can be performed at appropriate energydensity by shifting the focal point of the laser beam in an optical axisdirection from the surface of the structure (defocusing).

Moreover, when the laser beam is to be actually defocused, it wasconfirmed that defocusing to the negative side obviously improvedcoating removing performance than defocusing to the positive side. Forexample, if the surface to be treated was arranged on the positive sideby 20 mm (far distance), smoke was generated from the coating surface,and coating removal became uneven or insufficient but if the surface tobe treated on the negative side was arranged similarly by 20 mm (neardistance), laser abrasion strongly occurred on the coating surface, andefficient coating removal could be realized. The reason is considered tobe that, when the laser beam is irradiated to the removed matter peeledoff the coating surface and flying, the size of the laser beam becomesclose to the size of the removed matter in the vicinity of the focalpoint position, and thus, a moment when much of laser power is shieldedoccurs. The arrangement of the irradiation surface in front of the focalpoint will be referred to as “negative focus” below.

When the laser head is to be moved manually, it is difficult to keep adistance to the surface to be treated constant. Thus, this laserirradiation apparatus is preferably configured such that the distance tothe surface to be treated is made constant (preferably negativefocusing) by the length of the attachment of the laser head. Moreover,the length of the attachment may be made adjustable so as to adjust thenegative focus amount. Furthermore, by making the focal distance of thelaser beam settable as appropriate in addition to the attachment orwithout the attachment so that the negative focusing amount can beadjusted in accordance with the state of a coated matter (coating) forthe focal distance of the laser beam. Furthermore, a surface distancemeasuring means may be provided in order to keep the distance to thesurface to be treated within a predetermined range instead of theattachment or in addition to the attachment.

In the optical system of this laser head, a wedge prism rotatable aroundthe optical axis and a rotation driving means for rotating it arepreferably employed, whereby the laser beam can be irradiated so as tohave a conical shape flared toward the end. If the surface region as atarget is substantially flat and the optical axis becomes substantiallyperpendicular to this surface, a continuous trajectory of an irradiationpoint of the laser beam on the surface becomes a circular shape aroundan intersection between the optical axis and the surface and having adeflection amount of the wedge prism as a radius. Here, circularscanning of the irradiation point of the laser beam is referred to as“circular scanning” with respect to conventional linear scanning. Whenthe worker holds this laser head for a certain period of time orreciprocally moves it vertically or horizontally as necessary, a coatingin a specific range or a wide range can be efficiently removed in ashort time by laser abrasion.

Moreover, in the optical system of this laser head, the wedge prismrotatable around the optical axis and the deflecting means can beemployed, and the laser beam can be irradiated so as to have a conicalshape flared toward the end (may be partially hollow). For thedeflecting means, a wedge prism is preferably used, whereby thecontinuous trajectory of an irradiation point of the laser beam on thesurface has a shape in which a second circle having a deflection amountof a second wedge prism (second wedge prism) as a radius continuouslyrotates around a moving point on a circumference of a first circlehaving a deflection amount of a first wedge prism (first wedge prism) asa radius. If the irradiation point of the laser beam is continuouslyscanned for a certain period of time while the optical axis is fixedwith respect to the surface, the continuous trajectory can be considereda substantial annular or circular plane, and substantially uniform laserirradiation can be realized.

If the radius of a circle when the laser beam is used for circularscanning or the scanning method of the laser beam is changed, it isnecessary to change arrangement of the scanning optical system or tochange the configuration, but in the present invention, in the scanningoptical system of the laser head, since the replaceable optical unitincluding various optical members and the body portion including atleast the driving means is configured to be detachable by simpleoperation from the body portion of the laser head, the irradiationcondition of the laser beam can be also easily changed.

In the present invention, if the attachment is to be added to the laserhead, a closed space can be formed between the housing of the laser headand the surface so as to prevent scattering of the removed matter of acoating containing harmful substances to the environment and humanbodies. By providing the suctioning means in addition to the attachment,the removed matter can be suctioned in the closed space. This attachmentis preferably provided with an expansion/contraction mechanism so as tobe capable of expansion/contraction in accordance with setting. As aresult, a distance from the housing to the surface during a work can bekept constant. Moreover, at least a part of the attachment isconstituted by a deformable joint so that coating removal can beperformed even in a complicated structure, and an appropriate reflectingmeans is provided. As a result, the housing of the laser head can bebrought into contact with the surface by an arbitrary angle with respectto a normal line of the surface. Moreover, the attachment may beconfigured to have a mirror for irradiating the laser beam to a sidesurface of a protrusion so that a coating can be removed not only fromthe flat surface but also from the protrusion on the surface.

Moreover, the laser irradiation apparatus may be configured to beconnectable to a server via a network. In such a system, the serveracquires information relating to the state of the surface detected by asensor mounted on the laser head, and a laser irradiation conditionsuitable for the coating removal can be selected in accordance with thestate of the surface and can be transmitted to the laser irradiationapparatus.

Each of embodiments of the present invention will be explained below byreferring to the attached drawings. However, the present invention isnot limited to the following examples.

First Embodiment

A laser irradiation apparatus of a first embodiment is a laserirradiation apparatus including a small-sized and light-weightedportable laser head for removing a coating on a surface 20 of astructure and collecting the removed matter without scattering.

FIG. 1 is an outline configuration diagram of the laser irradiationapparatus of the first embodiment. This laser irradiation apparatusincludes a laser oscillator 1, a fiber 2, a laser head 3, a suction hose8, and a suction source 9 and may also include a gas supply source 11and a gas hose 12. The laser head 3 is a small-sized and light-weightedportable one, connected to the laser oscillator 1 via the fiber 2, andcan be handled at a work site.

Moreover, the laser oscillator 1, the suction source 9, and the gassupply source 11 are also apparatuses configured to be transportable andmovable and may be mounted on various types of vehicles 100 (a carriage,a vehicle, a barge, a mono-rack (including a monorail and a conveyer)and the like). In this laser irradiation apparatus, irradiationconditions such as an output of laser, a focal position, a beam width, ascanning speed and the like can be set as appropriate in accordance witha type, a nature and the like of the surface.

The laser oscillator 1 is constituted by an excitation source, a lasermedium, an optical resonator (mirror) and the like. The excitationsource may be either of a continuous wave oscillation (CW) type or apulse oscillation type, and an ark lamp, a flash lamp and the like canbe used. Moreover, a driving means for driving by application of anexcitation current and the like in accordance with a light source to beused may be provided. For the laser medium, a solid laser (ruby laser,YAG laser and the like) or semiconductor laser (laser diode) ispreferably employed. Particularly, fiber laser is preferably used as thesolid laser. The laser medium is not particularly limited and gas laser(CO₂ laser, eximer laser and the like), liquid laser (dye laser) and thelike may be used other than them. Note that the laser outputted from thelaser oscillator 1 is transmitted to the laser head 3 via the fiber 2for transmission.

By constituting the laser oscillator 1 by the fiber laser, variousadvantages can be obtained. In the fiber laser, a fiber added mainlywith rare earth ions is used as a laser medium, and wide-band opticalamplification is possible as compared with solid laser using YAGcrystals and the like. Since the fiber laser can be provided by windinga fiber in the oscillator, the laser oscillator can be constituted to besmall-sized and light-weighted and to be easy to be moved andtransported, and sufficient amplification can be obtained even if a gainper unit length is small.

Moreover, since the fiber laser has a surface area/volume ratio of thefiber larger than that of a bulk-type solid laser and has an excellentheat radiation property, air cooling can be employed as a cooling methodto make it a simple configuration can be employed. Since a numericalaperture NA is small, a condensing diameter can be easily made smaller.Moreover, since the fiber laser has a shorter oscillation wavelength andan excellent beam quality as compared with CO₂ laser, a focal depth canbe set larger. Furthermore, since the laser emitted from the fiber laserhas a high binding rate with a transmission fiber, even if a distancefrom the laser oscillator main body to the surface is far, the laser canbe transmitted with a smaller loss.

As described above, according to the fiber laser, the coating removingwork can be performed by transporting and appropriately moving the laseroscillator 1 itself to the vicinity of the surface of the structure(work site). However, the laser is irradiated to the surface by thelaser head 3 which can be handled, and it is only necessary that thelaser oscillator 1 itself is arranged in a range reachable from thefiber 2.

Since the present invention has an object of removal of a coating on thesurface, not drilling or cutting treatment of a workpiece, it is notnecessary to obtain a large energy density in one session of laserirradiation, and it is only necessary that the energy density enough toremove the coating in plural sessions of the laser irradiation can beobtained. Thus, in this embodiment, a high-output laser oscillator doesnot have to be used.

Moreover, in accordance with a type of the structure or the coating tobe a target and an entire configuration of the apparatus, either one ofthe CW-type laser and the pulse-type laser may be selected.Particularly, the CW-type laser requires large electric power to acquiredesired irradiation energy as compared with the pulse-type laser, butits cost is low, which is preferable. According to the inventors, it wasconfirmed that in laser irradiation per unit time and unit area, theCW-type laser has less thermal damage applied on an undercoat or a basematerial than the pulse-type laser, and the surface after the coatingremoval is smoother.

As described above, by employing the CW-type laser, it is likely thatpainting processing after the coating removal is facilitated, which ispreferable. However, this embodiment is not limited to the CW-type laserbut either one of the CW-type laser and the pulse-type laser may beselected in accordance with the type of the structure or the coating asa target and the entire configuration of the apparatus and the like.

The laser head 3 is an apparatus for irradiating the laser outputted bythe laser oscillator 1 and transmitted via the fiber 2 toward thesurface 20 of the structure, for removing the coating on the surface 20,and for suctioning the removed matter and is configured to be capable ofbeing handled at a work site. The laser head 3 has an optical system 4,a suctioning means 31 for suctioning a removed matter 60, a housing 32accommodating them, and an attachment 5 mounted on a tip-end of thehousing 32. Moreover, the laser head 3 may have a shielding member (notshown) for protecting the optical system 4 from the removed mattergenerated from a laser irradiation point.

Moreover, other than the above, a gas blowing means 34 for blowing a gas70 to the vicinity of the irradiation point of the surface 20, a controlunit 35 for controlling the optical system and the like, an operatingunit 36 into which operation from the worker is inputted, an auxiliaryirradiation means 37 for promoting ablation by irradiation of the laserbeam, a sensor group 7 including a contact proximity sensor, a coatingvisualizing sensor, a vibration detection sensor and the like, and apower supply unit (not sown) may be included. A specific configurationof the sensor group 7 will be described later by using FIG. 11.

The laser head 3 can appropriately set strength of the laser irradiationand the like by changing the output of the laser oscillator 1. Moreover,the laser head 3 is configured to be capable of appropriately settingthe irradiation condition such as a focal position, a beam width, ascanning shape and the like by the optical system 4 in accordance withthe state and the nature of the structure or the surface.

A laser beam 30 irradiated from the laser head 3 preferably has anoutput of 100 to 2000 W and a wavelength of 500 nm or more orparticularly preferably has an output within a range of 200 to 500 W anda wavelength within a range from 1060 to 1100 nm. Moreover, energydensity per unit time at a focal point can be designed as appropriate inaccordance with a material and a state of the surface and irradiationtime but it is preferably within a range of 1.25×10⁻⁴ to 5×10⁻⁴ J/μm².Note that a spot diameter of the laser beam may be set as appropriate interms of a relationship with energy density and a dimension of aworkpiece but it preferably has a diameter within a range of 20 to 200μm.

The optical system 4 is constituted by a combination of a lightcollecting element, a reflecting element, a refracting element, adriving means and the like, for example, and focuses the laser beamemitted from an emitting end of the fiber 2 and irradiates the laserbeam 30 to the surface 20 and is also capable of scanning theirradiation point of the laser beam 30 on the surface 20 linearly or ina curved manner. An appropriate configuration can be employed for theoptical system 4, but in order to make the laser head small and simple,it preferably has a configuration of deflecting the laser beam using apermeable refracting element. A specific configuration of the opticalsystem 4 will be described later by using FIGS. 3 and 5.

The housing 32 is preferably configured to have a small size and a shapewith excellent gripping performance so that the worker can grip iteasily.

When the laser beam 30 is irradiated to the surface 20, the irradiationpoint enters a high-temperature and high-pressure state in whichablation (melting/transpiration) occurs, and a coating is removed by anaction of this ablation. When the laser beam is irradiated, a removedmatter is generated from the vicinity of the irradiation point. In thisembodiment, since the suctioning means 31 is provided on the laser head3, the removed matter 60 is basically collected via a suction port 33 ofthe suctioning means 31, but a part of the removed matter 60 is drawn toa direction of the optical system 4 and might adhere to the lens of theoptical system 4. Thus, on the laser head 3, a shielding member (notshown) for protecting the optical system 4 from the removed mattergenerated from the laser irradiation point is preferably provided.Regarding the shielding member, a shielding member arranged between theemitting end face of the optical system 4 and the surface to be treatedis preferably provided. The shielding member may be a plate-shapedmember in which an opening is provided only at an optical axis portionor may be a plate-shaped member without an opening having lightpermeability to the laser beam (protective glass and the like).

The attachment 5 is preferably attached detachably to a tip-end of thehousing 32 of the laser head and is brought into close contact with thesurface 20 so as to form a closed space. Here, the closed space ispreferably a fully closed and sealed space but may have a slight gap. Itis only necessary that the attachment 5 is configured to be able to movethe laser head 3 in contact with the surface 20 but it is preferablyconfigured to be capable of being brought into contact with a curvedsurface. For example, the attachment 5 may be formed of a soft anddeformable resin, or a sliding assisting means may be provided on a sidein contact with the surface of a tip-end of the attachment. The slidingassisting means may be a tire or a roller, or a brush-like or acurtain-like member formed of a flexible member may be provided.

Moreover, it is preferable that the attachment 5 has anexpansion/contraction mechanism, and a distance d (see FIG. 2A) from theprincipal point of the scanning optical system 4 to the surface 20 canbe set appropriately. For the expansion/contraction mechanism of theattachment 5, a zoom mechanism, an autofocus mechanism and the like of ageneral camera may be used, for example. In the attachment 5, adeformable joint portion (flexible tube) may be formed at least at apart thereof so that an orientation of an optical axis L of the laserhead 3 can be changed with respect to the normal line of the surface 20.

In this laser head 3, an interval between the laser head 3 and thesurface 20 can be set as appropriate by the expansion/contractionmechanism of the attachment 5 mounted on the laser head tip-end.Moreover, the focal distance of the laser beam 30 can be set asappropriate by the optical system 4.

FIG. 2A is an explanatory view illustrating a positional relationshipbetween a focal point F and the irradiation point. The inventor found asthe result of keen studies that a coating can be removed moreefficiently by moving the position of the surface 20 to the negativeside in the direction of the optical axis L from the focal point F(negative focusing) and by arranging the surface 20 to be treated infront of the focal point rather than arranging the surface 20 at thefocal point F of the laser beam 30.

Assuming that, with the focal point F as a reference, a distance to theirradiation point (irradiation spot) P of the laser beam 30 on thesurface 20 is Δf (defocusing amount), the defocusing amount (in the caseof negative) is specified by a relationship of the focal distance f fromthe principal point of the optical system 4 to the focal point F and thedistance d from such principal point to the surface 20 (hereinafterreferred to as an “inter-surface distance”). Note that, in this figure,the inter-surface distance d and the focal distance f starts from theemitting-side end of the optical system 4 in the housing 32 for theconvenience of explanation, but actually the principal point of theoptical system shall be the start point. The defocusing amount Δf isacquired by the distance d—the focal distance f, and it is preferablyset in a range of 0 to −30 mm, or more preferably set within a range of−5 to −25 mm. Note that if the laser beam is deflected, the surface tobe treated is preferably arranged within a range of 0 to −30 mm withrespect to the focal point along the optical path of the deflected laserbeam, and more preferably set within a range of −5 to −25 mm.

In this embodiment, the defocusing amount Δf (in other words, a positionof the focal point to the surface to be treated) can be set asappropriate by changing the inter-surface distance d, and theinter-surface distance d when the laser head is in contact can bechanged as appropriate by the attachment 5 provided with theexpansion/contraction mechanism, for example. With a configuration inwhich the focal distance f can be changed as appropriate by the opticalsystem 4 (variable focusing mechanism), the position of the focal pointcan be changed without using the expansion/contraction function with theattachment in contact. Moreover, the defocusing amount may be changed asappropriate by using both the expansion/contraction function of theattachment and the variable focusing mechanism of the optical system.

By referring to FIG. 1 again, the suctioning means 31 suctions theremoved matter 60 (powder dusts of the coating, micro fractions)generated from the irradiation point of the laser beam 30 via thesuction port 33 by a negative pressure applied by the suction source 9.The suction source 9 is a pump for applying a suction force, forexample, and a treatment chamber for treating the suctioned removedmatter 60, an air-exhaust filter and the like may be also provided. Theremoved matter 60 suctioned from the suctioning means 31 may becollected by the suction source 9 via the suction hose 8, while theremaining harmless air and the like may be exhausted via the air-exhaustfilter. The suctioning means 13 suctions the removed matter 60 generatedfrom the irradiation point of the laser beam via the suction port 33 inthe closed space formed by the attachment 5.

The gas blowing means 34 is to blow the gas supplied from the gas supplysource 11 via the gas hose 12 to the vicinity of the irradiation pointof the laser beam 30 and has an action of guiding the removed matter 60toward the suction port 33 of the suctioning means 31 so that theremoved matter 60 (also including powder dusts of the coating, microfractions, smoke and the like) generated from the vicinity of theirradiation point by ablation does not interfere with the laserirradiation in order to irradiate the laser beam 30 to the surface morereliably. Moreover, it may also be used for preventing or reducingcontamination or the like of the emitting end surface of the opticalsystem 4 (lens) inside the housing 32 by the removed matter asnecessary.

The gas supply source 11 is constituted by a tank, a bomb, a compressorand the like, for example. The gas can be selected as appropriate inaccordance with the state, the material, the nature and the like of thework environment or the surface. For example, dry air, nitrogen, carbondioxide, inactive gas (helium, neon, argon and the like, for example) ora charged gas as a measure against static electricity may be used. Whena toxic reaction gas might be generated from the surface, nitrogen or aninactive gas is preferably supplied or an active gas for neutralizingthe reaction gas is preferably supplied in order to reduce generationthereof. Moreover, not limited to the gas, but a liquid (including mist(steam)) may be blown. The liquid includes water for heating thesurface, a treatment agent for promoting ablation, chemicals such as anundercoat protecting agent after the coating removal and the like.

Note that the fiber 2, the suction hose 8, the gas hose 12, and a powercable (not shown) connecting the laser oscillator 1, the suction source9, and the gas supply source 11 to the laser head 3 may be bundled intoone integral cable 25 so that the worker can handle the laser head 3easily at the work site.

Moreover, when the laser beam is irradiated, the removed mattergenerated from the vicinity of the irradiation point may be charged withstatic electricity. Since such removed matters can easily adhere to thelens of the optical system, they might reduce the life of the lens.Thus, an antistatic means is preferably provided in the laser head. Asthe antistatic means, for example, a gas blowing means can be used tosupply gas containing ions in accordance with a charged amount of theremoved matter so as to remove static electricity. Alternatively, asdescribed above, the shielding member for shielding adhesion of theremoved matter to the optical system can be used, and a conductivemember may be provided at least at a part of the shielding member so asto remove the removed matter charged with static electricity. Moreover,a member for removing static electricity may be provided at anappropriate position in the laser head separately from the shieldingmember. Moreover, the antistatic means may remove static electricityfrom the removed matter flying to the periphery of the optical system bysupplying magnetism.

The auxiliary irradiation means 37 applies various types of energy tothe vicinity of the irradiation point in order to assist ablation asnecessary (for example, when the coating on the surface 20 is thick andrequires laser irradiation for removal for a long time). The auxiliaryirradiation means 37 may be constituted capable of irradiating light,heat, ultrasonic waves, microwaves or laser, for example. Specifically,a halogen lamp or a metal halide lamp capable of heating by lightirradiation, an ultrasonic heater, a magnetron type microwaveoscillator, carbon-dioxide gas laser for surface heating and the likecan be employed. Moreover, the auxiliary irradiation means 37 can beillumination for photographing a state of the surface by a CCD camera(reference numeral 73 in FIG. 11).

The control unit 35 has a function for controlling the scanningmechanism and the variable focusing mechanism of the optical system 4,the expansion/contraction mechanism of the attachment 5, the suctioningmeans 31, the gas blowing means 34, the operating unit 36, the auxiliaryirradiation means 37 an the like. The control unit 35 may be configuredto realize various types of processing by allowing hardware and aprogram to collaborate with each other or may be constituted by anexclusive processing circuit. In the same figure, the control unit 35 isprovided in the laser head body but may be provided separately from thelaser head body, and a terminal connected wirelessly or by wire (seereference numeral 82 in FIG. 14) may be configured as a control unit forcontrolling the laser head 3, for example.

The operating unit 36 has a function for receiving operation of theworker and outputting it to the control unit 35. Moreover, it may have afunction for displaying the result of the operation, a state of coatingremoval, parameters of the laser and the like. The operating unit 36 isconstituted by various switches, knobs, a software keyboard, a displayapparatus and the like.

As described above, according to the laser irradiation apparatus of thefirst embodiment, a coating on the surface can be removed at the worksite by using the transportable and movable laser irradiation apparatus,and the removed matter can be collected. Since the portable laser headcapable of being handled and connected to the laser oscillator via thefiber is used, the coating removing work becomes easy for the worker.Moreover, the laser output and wavelength can be set as appropriate inaccordance with the state of the surface, and laser irradiation suitablefor the coating removal can be performed.

Moreover, according to the optical system of this laser head, theirradiation conditions such as the position of the focal point, the beamwidth, the scanning speed and the like can be set as appropriate, andlaser irradiation suitable for the coating removal can be performed.Moreover, by using the suctioning means and the attachment provided onsuch laser head, the coating can be removed and the removed matter canbe efficiently suctioned without scattering. By setting theinter-surface distance by the expansion/contraction mechanism of theattachment as appropriate, the defocusing amount can be adjusted inaccordance with the state of the surface, and ablation suitable for thecoating removal can be realized.

Moreover, according to the attachment of this laser head, an appropriatespace for suctioning of the removed matter can be ensured, and there islittle concern that the suction port is clogged by concentrated removedmatters. Moreover, leakage and scattering of the laser beam can beprevented, and safety for the worker can be ensured. Since the workermoves the laser head while bringing this attachment into contact withthe surface, the inter-surface distance d can be kept constant, and theremoving work can be proceeded with efficiently.

Another embodiment of the optical system inside of this laser head willbe explained below. First, as a second embodiment, a configuration of alaser head using one wedge prism for a scanning mechanism will beexplained (FIGS. 3 and 4), and then, as a third embodiment, aconfiguration of a laser head using a wedge prism and a deflecting meansfor the scanning mechanism will be explained (FIGS. 5 to 7). However,the present invention is not limited to the following examples.

Second Embodiment

In the second embodiment, a wedge prism rotatable around an optical axisand a driving means for rotating it are used in the optical system, andthe laser beam is irradiated having a conical shape (side surface)flared to the end. A continuous trajectory of the irradiation point ofthe laser beam on the surface becomes a circle Cl around an intersectionbetween the optical axis and the surface and having a deflection amountof the wedge prism as a radius r1. Hereinafter, the optical system thatcan scan the irradiation point by a driving mechanism or the like willbe also referred to as a scanning optical system.

Moreover, when the worker holds this laser head for a certain period oftime or reciprocally moves it vertically or horizontally as necessary, acoating in a specific range or a wide range can be efficiently removedby laser ablation in a short time.

FIG. 3 is an outline configuration diagram of the scanning opticalsystem of the laser head of the second embodiment. This laser head 3A isconnected to the laser oscillator 1 via the fiber 2 and can be handledat the work site. In this embodiment, the scanning optical system 4includes a fiber connection portion 41, a light collecting means 42, afirst wedge prism 43, a support member 44, and a driving means 49.

The fiber connection portion 41 is an optical element (laser emittingcollimator (quartz lens, for example) mounted at an emitting end of thefiber 2 and emits the laser beam transmitted via the fiber 2 toward thelight collecting means 42 as parallel light.

The light collecting means 42 is a light-collecting optical systemconstituted by one or more lenses and collects the laser beam outputtedfrom the fiber connection portion 41 at high energy density andirradiates it as the laser beam 30 to the surface 20. Regarding thelight collecting means 42, a focal distance, a focal depth, and a beamspot diameter of the laser beam 30 can be set as appropriate.

The first wedge prism 43 is an optical element for deflecting theincident laser beam at a deflection angle θ with respect to the opticalaxis L. The first wedge prism 43 (and the light collecting means 42) issupported by the support member 44. In this embodiment, the wedge prismis employed as an optical member for deflecting an optical path of thelaser beam. As a result, the optical path of the laser beam becomessimple without repeating reflection as compared with use of the opticalmember such as a galvano-mirror and thus, the configuration of the laserhead can be made small and simple.

The driving means 49 rotates the first wedge prism 43 by rotating thesupport member 44 at a predetermined rotation speed w around the opticalaxis L. For the driving means 49, an appropriate configuration such as amotor, a rotary actuator and the like can be employed, but in order tomake the configuration of the laser head small and simple, a hollowmotor that can be arranged around the optical axis is preferablyemployed.

According to such scanning optical system 4, the irradiation point P ofthe laser beam 30 (including the irradiation spot) appears at a positionof a distance r from an optical axis intersection O on the surface 20.The distance r is a deflection amount on the basis of the deflectionangle θ of the first wedge prism 43, the distance from the first wedgeprism 43 to the surface 20 and the like.

Moreover, a shielding member 48 for protecting the first wedge prism 43can be employed for shielding the removed matter generated from thevicinity of the irradiation point of the laser beam. The shieldingmember 48 is configured to be fixed to the first wedge prism 43 or thesupport member 44 and rotatable with them and has an opening throughwhich the laser beam 30 deflected in accordance with the deflectionangle of the wedge prism is passed at an appropriate position. In thisembodiment, the suctioning means (reference numeral 31 in FIG. 1, forexample) and the attachment (reference numeral 5 in FIG. 1, for example)are not provided, and the removed matter generated from the laserirradiation point P is scattered to the periphery, but since theshielding member 48 is provided, the wedge prism can be protected fromthe removed matter peeled off and scattered from the surface 20.Moreover, it may be so configured that a conductive member is providedat least at a part of the shielding member 48 so as to actively removethe removed matter charged with static electricity. Moreover, it may beso configured that, by using the gas blowing means (see referencenumeral 34 in FIG. 1 or FIG. 11) as an antistatic means, staticelectricity can be removed by supplying a gas containing ions from sucha gas blowing means in accordance with the charged amount of the removedmatter.

In this embodiment, it is only necessary that energy density enough toremove the coating in several sessions of circular scanning can beapplied in removing the coating and thus, the focal point does not haveto be matched with the actual irradiation point of the laser beam,unlike the conventional laser working apparatus intended for drilling,cutting, spot welding of the metal and the like. In the circularscanning, since an optical path length of the laser beam 30 becomessubstantially equal at each point on the substantially circulartrajectory, the distance between the focal point and the actualirradiation point does not change in the rotary scanning, unlike thelinear scanning, and constant irradiation energy can be irradiated.Moreover, in order to effectively use the energy of the laser, theposition of the focal point is preferably set close to the depth fromthe surface (defocusing to the negative side). Furthermore, the focaldepth may be set deeper to some degree. As a result, coating removaltreatment can be performed also for the surface of a structure with aprotrusion, a step or a depth.

FIG. 2B is a diagram for roughly explaining a positional relationshipbetween the focal point and the irradiation point when the laser beam isdeflected. When the laser beam is deflected by the deflection angle θwith respect to the optical axis L1 by the optical system 4 having thewedge prism, a focal point F1 and an irradiation point P1 on the opticalpath L1 without deflection are moved to positions corresponding to F2and P2 on a new optical path L2 having the deflection angle θ. Thus,when the defocusing amount Δf is set on the basis of F2, the surface tobe treated is preferably arranged at a position of P2 within a range of0 to −30 mm with respect to the focal point F2, or more preferablyarranged within a range of −5 to −25 mm. Note that FIG. 2B uses aprincipal point S as a reference for deflection for convenience ofexplanation that the focal distance f when the laser beam is deflectedgoes along the optical path of the deflected laser beam, but it might bedifferent from the principal point in an actual optical system.

Moreover, the laser head is brought into contact with the surface by theattachment 5, and the distance from the scanning optical system to thesurface is constant all the time. From this point of view, too,employment of the circular scanning with the unchangeable optical pathlength is preferable. Furthermore, in this embodiment, since theirradiation point of the laser beam is subjected to rotary scanning in acircular state around the optical axis intersection, even if the laserbeam is reflected from the surface, there is no concern that returnlight enters the laser head and damages the fiber 2. In addition, inthis embodiment, since the antistatic means is provided in the laserhead, the removed matter charged with the static electricity isprevented from adhering to the optical system, or static electricity canbe removed from the removed matter.

FIG. 4 is an explanatory diagram illustrating a trajectory of the laserirradiation point by the laser head of the second embodiment. When theoptical axis L and the surface 20 are substantially perpendicular andthe surface 20 is a substantially flat plane without curve orirregularity, since the first wedge prism 43 rotates around the opticalaxis L at the rotation speed ω, the irradiation point P of the laserbeam becomes a moving point moving at the rotation speed ω on thecircumference of the circle having the radius r around the optical axisintersection O on the surface 20.

In other words, the irradiation point P draws a trajectory of the circleC (including a substantially circular shape) around the optical axisintersection O. Therefore, if the laser beam 30 is irradiated to thesurface 20 of the structure by using the laser head 3A of the secondembodiment, the coating is removed by laser ablation along thecircumference of the circle C on the surface 20. Note that, forfacilitation of explanation, the circumference of the circle C isexpressed as a line without width in the figure, but actually, the laserbeam 30 has a width of the spot diameter. Moreover, the radius r ispreferably set so as to be 5 to 200 mm.

By moving the laser head 3 automatically or by operation of the workerat a certain speed in a vertical direction or in a horizontal directionin parallel with the surface 20 while the circular scanning as the shapeof the circle C is performed, the trajectory of the irradiation point Psubstantially becomes a band shape. As describe above, since theirradiation point P can be scanned substantially uniformly with respectto the surface 20, the coating in a wide range on the surface 20 can beefficiently removed in a short time. In the figure, the laser head 3A ismoved linearly in a specific direction but it may be moved in a Z-shapedstate, a zigzag state, an arc state or a spiral state, for example, inaccordance with a type of the structure, a state of the surface and thelike.

Note that, in this figure, for facilitation of explanation, a shape inwhich the circle C continues in a moving direction of the laser head isschematically illustrated. However, actually, the irradiation point isscanned circularly while the laser head (that is, the optical axisintersection) is moved, the trajectory of the irradiation point Pbecomes a shape of a coil which is an open curve not that the circle Cwhich is a closed curve continues. More strictly, the trajectory of theirradiation point P becomes a trajectory of an end point of a radiusvector r rotating at the rotation speed ω.

Specifically, if, at time t=0, for example, the irradiation point P ison the Y-axis and starts rotation at an angular speed ω (only circularscanning), a trajectory (Px, Py) of the irradiation point at the time tis expressed by the following formula:

Px=r sin ωt

Py=r cos ωt   [Formula 1]

Furthermore, if the worker moves the laser head at a certain speed V ina direction of a vector having an angle Φ to the X-axis, for example,the trajectory (Px, Py) of the irradiation point at the time t isexpressed by the following formula:

Px=r sin ωt+Vt cos Φ

Py=r cos ωt+Vt sin Φ  [Formula 2]

Particularly when the laser head is moved in the horizontal direction(X-axis direction), it can be expressed as follows:

Px=r sin ωt+Vt

Py=r cos ωt   [Formula 3]

Moreover, this figure illustrates an instance in which the optical axisL and the surface 20 are substantially perpendicular, the surface 20 isflat, and the trajectory of the irradiation point P is substantiallycircular. If the laser head is held with inclination to the normal lineof the surface (that is, the optical axis L and the surface 20 are notsubstantially perpendicular), the trajectory of the irradiation point Pbecomes oval (including a shape of substantially oval).

Moreover, if the surface 20 has irregularity formed or has a curve, thetrajectory of the irradiation point P becomes a distorted circle or anoval. In these cases, strictly speaking, the optical path length of thelaser beam at each of the irradiation points on the trajectory becomesdifferent from each other and thus, the actual irradiation point mightbe somewhat deviated from the preset focal point. In this case, thefocal depth is preferably set larger to some degree (within a range of achange amount of the optical path length). As a result, desired energydensity for coating removal can be cumulatively applied by severalsessions of rotary scanning.

If the trajectory of the irradiation point P becomes an oval shape,strictly speaking, the optical path length of the laser beam at each ofthe irradiation points on the trajectory becomes different from eachother and thus, the present focal point might be deviated from a desiredposition. In this case, the focal depth is preferably set larger to somedegree (within a range of a change amount of the optical path length) inadvance. Since desired energy density for coating removal can becumulatively applied in several sessions of rotary scanning, there is noproblem even if the optical path length changes to some degree.

As described above, according to the laser head of the secondembodiment, since the irradiation point of the laser beam is subjectedto rotary scanning in a circular state around the optical axisintersection, by moving this laser head as appropriate, it becomessubstantially planar scanning, and a coating in a wide range can beefficiently removed in a short time.

Moreover, since the wedge prism is used as a scanning element fordeflecting the optical path of the laser beam, the optical path of thelaser beam becomes simple without repeating reflection as compared withuse of the optical element such as a galvano-mirror and thus, thescanning mechanism can be made small and simple. As a result, asmall-sized laser head that can be handled at the work site can berealized with a low cost. Moreover, in such circular scanning, since theoptical path length does not change, the configuration of the laser headcan be made simple.

Moreover, the focal depth may be set large to some degree, whereby thecoating removal treatment can be performed also for a surface of astructure with a protrusion, a step or a deep depth and a corner part ofthe structure. Moreover, required energy density for laser ablation canbe applied in several sessions of circular scanning, and a coating canbe efficiently removed. Furthermore, according to such circularscanning, if the laser beam is reflected from the surface, there is noconcern that return light enters the laser head and damages the fiber 2.

Third Embodiment

In the above-described second embodiment, one wedge prism is used forthe scanning optical system. On the other hand, in a third embodiment, awedge prism rotatable around an optical axis and a deflecting means areused for the scanning optical system, and the laser beam is irradiatedso as to have a conical shape flared to the end (may be partiallyhollow). The deflecting means may be a reflective optical element suchas a mirror, but a permeable optical element such as a wedge prism ispreferably employed. Hereinafter, a case in which the wedge prism isused as the deflecting means will be explained. A continuous trajectoryof the irradiation point of the laser beam on the surface has a shape inwhich a second circle having a deflection amount of a second wedge prism(second wedge prism) as a radius continuously rotates around a movingpoint on a circumference of a first circle having a deflection amount ofa first wedge prism (first wedge prism) as a radius. If the irradiationpoint of the laser beam is continuously scanned for a certain period oftime while the optical axis is fixed to the surface, the continuoustrajectory can be considered a substantially annular or circular plane,and substantially uniform laser irradiation can be realized.

FIG. 5 is an outline configuration diagram of the scanning opticalsystem of the laser head of the third embodiment. This laser head 3B hasa second wedge prism 45, a support member 46, and a transmitting means47 as an additional configuration of the scanning optical system inaddition to the configuration of the laser head 3A of the secondembodiment. Moreover, the laser head 3 may have a shielding member (notshown) for protecting the scanning optical system from the removedmatter generated from the laser irradiation point as necessary. In thelaser head 3B of the third embodiment, the configurations similar tothose in the laser head 3A of the second embodiment will be given thesame reference numerals, and detailed explanation will be omitted.

The second wedge prism 45 deflects the optical path of the laser beamfurther by a deflection angle θ2 with respect to an optical path M(hereinafter also referred to as a rotation reference axis M) of thelaser beam deflected by a deflection angle θ1 with respect to theoptical axis L by the first wedge prism 43. The second wedge prism 45 issupported by the support member 46.

The transmitting means 47 links the support member 44 including thefirst wedge prism 43 and the support member 46 including the secondwedge prism 45 with each other and transmits a driving force from thedriving means 49. As the driving means 49, a gear mechanism for which anappropriate rotation ratio can be set may be used, for example.

In this embodiment, the first wedge prism 43 is rotated at a rotationspeed ω1 by rotating the support member 44 around the optical axis L bythe driving means 49, and the second wedge prism 45 is rotated at arotation speed ω2 by rotating the support member 46 around the opticalaxis L via the transmitting means 47 linked with the support member 46.

Moreover, considering the surface 20 substantially perpendicular to theoptical axis L, when the two wedge prisms are rotated around the opticalaxis L, an intersection Q between the surface 20 and the rotationreference axis M appears at the position of the distance r1 on thesurface from the optical axis intersection O. And the irradiation pointR (including the irradiation spot) appears at the position of thedistance r2 on the surface from the intersection Q.

Note that the distance r1 is a deflection amount on the basis of thedeflection angle θ1 of the first wedge prism 43 and the distance fromthe first wedge prism 43 to the surface 20 and the like, and thedistance r2 is a deflection amount on the basis of the deflection angleθ2 of the second wedge prism 45 and the distance from the second wedgeprism 45 to the surface 20 and the like.

In this figure, the configuration in which the driving means 49 directlyapplies a rotary driving force to the first wedge prism 43, and thetransmitting means 47 indirectly applies a rotary driving force by thedriving means 49 to the second wedge prism 45 was explained, but this isnot limiting. Different rotary driving forces may be applied to thewedge prisms, respectively, by two driving means, or the rotary drivingforce directly applied to the transmitting means from the driving meansmay be applied to each of the wedge prisms. It is only necessary thatthe first wedge prism 43 and the second wedge prism 45 can rotate atdifferent rotation speed.

FIG. 6 is an explanatory diagram illustrating an example of a trajectoryon a treatment plane of the laser irradiation point according to thethird embodiment. This figure illustrates a case in which the opticalaxis L and the surface 20 are substantially perpendicular, and thesurface 20 is a substantially flat plane without curve or irregularity.Since the rotation reference axis M is a radius vector rotating aroundthe optical axis L at the rotation speed ω1, the intersection Q betweenthe rotation reference axis M and the surface 20 becomes a moving point(hereinafter also referred to as a moving point Q) moving at therotation speed ω1 on the circumference of the circle C1 with the radiusr1 around the optical axis intersection O. And an irradiation point R ofthe laser beam becomes a moving point moving at the rotation speed ω2 onthe circumference of the circle C2 with the radius r2 around the movingpoint Q.

Note that in this figure, for explanation, the trajectory of the circleC2 when the rotation reference axis M makes a round, that is, when themoving point Q on the circle C1 makes a round is schematicallyillustrated, and the circle C2 apparently has a shape continuing aroundeach point on the circle C1. However, actually, the moving point Q ismoving on the circle C1 and the irradiation point R moves around it, andthus, the trajectory of the irradiation point R has a shape like a coilring which is an open curve, not continuation of individual circles C2which is a closed curve. More strictly, the trajectory of theirradiation point R becomes a trajectory of end point of a radius vectorr2 further rotating at the rotation speed ω2 around the end point of theradius vector r1 rotating around the optical axis intersection O at therotation speed ω1 (that is, the trajectory of the end point of thevector r (r1+r2).

Note that, the rotation speed ω2 is preferably set sufficiently largerthan the rotation speed ω1, and a ratio between the rotation speed ω1and the rotation speed ω2 (rotation ratio ω2/ω1) is preferably larger atleast than 9/2.

Moreover, the rotation ratio (ω2/ω1) is preferably set so that aninitial position of the irradiation point R does not match the positionof the irradiation point R when the rotation reference axis M makes asingle or several rounds. Then, even if the rotation reference axis Mrotates several rounds, the C2 which is the trajectory of theirradiation point R does not overlap on the surface 20 and thus,substantially uniform scanning is made possible.

Moreover, while scanning of the shape of the circle C2 is performed,when the laser head 3B is moved in parallel with the surface 20vertically or horizontally at a certain speed automatically or byoperation of the worker, the irradiation point R can be scannedsubstantially uniformly with respect to a specific range of the surface20, and a coating in the specific range on the surface 20 can beefficiently removed in a short time.

FIG. 7 is an explanatory diagram illustrating another example of thetrajectory of the laser irradiation point by the laser head of the thirdembodiment. If scanning of the shape of the circle C2 is performedwithout moving the optical axis intersection O for a certain period oftime, as illustrated in this figure, a coating in a region of a ring C3with the circle C1 as a center curve can be also removed.

As described above, according to the laser head of the third embodiment,in addition to the effect of the second embodiment, since theirradiation point of the laser beam is scanned on an annular or circularplane, a coating in a specific range on the surface of the structure canbe efficiently removed in a short time. This embodiment is suitable forremoval of a coating in the periphery of a protrusion such as a bolt,for example.

Moreover, a radius of the center curve C1 and a width of the ring C3 areamounts depending on r1 and r2 corresponding to the deflection amountsof the wedge prism, respectively, and thus, by setting r1 and r2, thatis, the deflection angle θ1 of the first wedge prism and the deflectionangle θ2 of the second wedge prism as appropriate, a ring irradiationregion with various sizes and shapes can be set, and a shape of a circlewithout a region for irradiation at a center part can be also set.

For example, when a coating in the periphery of a circular protrusionlocated on a plane to be treated is to be removed, if a region forirradiation is provided by setting the deflection angle θ1 and thedeflection angle θ2 so that |r2−r1| becomes the radius of the circularprotrusion, only the periphery of the circular projection can bescanned. Moreover, by setting r2≧r1, a shape not a ring but an entirecircular surface without the region for irradiation at the center partcan be also scanned.

Fourth Embodiment

As a fourth embodiment, a replaceable attachment mounted on a tip-end ofthe laser head will be explained below. This attachment has a deformablejoint portion and a mirror with a changeable angle. As a result, thehousing of the laser head can be brought into contact with the surfaceby an arbitrary angle with respect to the normal line of the surface.Thus, it is suitable for a complicated work site in which a sufficientwork space cannot be ensured or an application for removing a coating ona periphery of a protrusion such as a bolt and a side surface of theprotrusion itself.

FIG. 8 is an outline configuration diagram of a laser head of the fourthembodiment. This attachment can be detachably attached to the tip-end ofthe housing 32 of the laser head and can be mounted on the laser head ofthe first to third embodiments. This figure is an example of beingattached to the housing tip-end of the laser head (FIG. 5) of the thirdembodiment.

This attachment 5B has a deformable joint portion (flexible tube) 53 andis configured such that its own shape is deformable in accordance withan angle with respect to a normal line of a surface 20B. In this figure,the attachment 5B is configured such that a laser head 3C issubstantially perpendicular to the normal line of the surface 20B. Theattachment 5B has a first mirror 51 and a second mirror 52 (see FIG. 9).However, the second mirror 52 may be removed depending on an application(if the laser beam is not to be irradiated to a side surface of aprotrusion, for example). Moreover, the laser head 3C may have ashielding member (not shown) for protecting a scanning optical systemfrom a removed matter generated from the laser irradiation point.

The first mirror 51 is configured such that the angle of the normal lineof the first mirror itself with respect to the optical axis L can bechanged as appropriate. As a result, as illustrated, the irradiationdirection of the laser beam can be changed to a direction of an incidentaxis Lb from an optical axis La. An angle between the optical axis Laand the incident axis Lb can be set arbitrarily, and though notparticularly limited, the angle is preferably set to 90°, for example.In this case, the trajectory of the irradiation point of the laser beamon the surface 20B is similar to the trajectory on the surface 20perpendicular to the optical axis L illustrated in FIG. 6.

FIG. 9 is an outline configuration diagram of a part of the attachmentof the fourth embodiment and illustrates it together with an opticalpath of the laser beam of the laser head 3C. As illustrated in thefigure, there is a protrusion 20C (a bolt, for example) on the surface20B, and the laser beam 30 enters while rotating around the rotationreference axis Mb rotating around the incident axis Lb deflected by thefirst mirror 51. The laser beam 30 closer to the incident axis Lb isirradiated to an upper surface of the bolt 20C, while the laser beam 30farther from the incident axis Lb is reflected by the second mirror 52provided on the attachment 5B and is irradiated to a side surface of thebolt 20C. As described above, by using this attachment, coating removalaround the protrusion which has been difficult can be easily performed.

As described above, according to the attachment of this embodiment,since the laser head can be brought into contact with the surface in anarbitrary orientation, the removing work can be easily performed even ina complicated and narrow structure in which handling is limited withouta need for the worker to take a forced attitude. Moreover, by mountingthis attachment to the laser head of the third embodiment, a coatingaround the protrusion on the surface and the side surface of theprotrusion itself can be efficiently treated.

FIG. 10 is an explanatory diagram illustrating still another example ofthe attachment of the laser head of the fourth embodiment. This exampleis a mode in which an attachment including a reflective mirror ismounted at a tip-end of the laser head provided with the scanningoptical system illustrated in FIG. 3. This example has a simplerstructure and can be used in a narrow part of a structure, for example,and can remove a coating, an adhering substance and the like on thesurface at a complicated spot, which has not been realized in aconventional blast method.

An attachment 5C is connected to a tip-end of the laser head housing 32,and the reflective mirror 51 is provided on the tip-end at apredetermined angle. The laser beam 30 irradiated having a conical shapefrom the scanning optical system of the laser head is reflected by thereflective mirror 51, and the laser irradiation point is scannedsubstantially circularly on an inner-side surface of the narrow part ofthe structure. The shielding member 48 for protecting the optical member(a prism, a lens, a mirror and the like) arranged on the emitting endside from the removed matter generated from the laser irradiation pointis preferably provided on an emitting end of the scanning opticalsystem. The shielding member 48 has a flat-plate shape, for example, andan emitting port 50 of the laser beam and is configured to rotate withrotation of the scanning optical system.

Moreover, in the attachment 5C, in order to protect the reflectivemirror 51 from the removed matter generated from the laser irradiationpoint, the gas blowing means 34 for supplying a gas flow to thereflective mirror 51 may be provided. The gas blowing means 34 blows thegas force-fed from the gas supply source, not shown, via the gas hose 12to the vicinity of the surface of the reflective mirror 51 and preventsadhesion of the scattered removed matter to the reflective mirror 51.

Fifth Embodiment

An example in which a sensor group and the like are provided in thelaser head of the first to fourth embodiments will be explained below.

FIG. 11 is an outline configuration diagram of a laser head of a fifthembodiment. This laser head is provided with various sensors as thesensor group 7 such as a contact proximity sensor 71, a surface statesensor 72, a monitoring sensor 73, a vibration detection sensor 74, aninter-surface distance measurement sensor 75 and the like. Note that thelaser head does not have to be provided with all of the sensor group 7,and the sensor group 7 may be employed by selection according to apurpose or one sensor may serve a plurality of functions.

The contact proximity sensor 71 is a sensor for detecting that theattachment 5 is in contact or approaching the surface 20. For such asensor, a pressure sensor mounted at a contact portion at the tip-end ofthe attachment with the surface to be treated, a sensor for measuringreflection strength of an emitted electric wave and the like, forexample, can be used or it may be so configured that contact with orproximity to the attachment is detected. The control unit 35 (it may bea management terminal (see reference numeral 82 in FIG. 14) separatefrom the laser head. The same applies to the following) can also controlsuch that irradiation of the laser beam is not allowed unless detectionis made by such a sensor. As a result, the laser beam is prevented frombeing emitted to other than the surface to be a target of the coatingremoval by mistake, and safety of the worker can be ensured. Moreover,in the case of a sensor for measuring the reflection strength of theemitted electric wave, it may be so configured that irradiation of thelaser beam is allowed only if the reflection strength exceeds apredetermined value. As a result, erroneous emission of the laser beamto human bodies and the like can be prevented.

The surface state sensor 72 detects a material (steel plate, aluminumand the like) of an undercoat of the surface 20, a state of a coating(floating, thickness), a rust state (area, degree), a corrosivesubstance, a stain, an adhesion state of fat and oil and the like.Moreover, a removed amount of a coating and the like may be detected.Specifically, a radiation temperature sensor, a visible-areaspectroscopic image sensor, a near-infrared camera and the like can beemployed. The monitoring sensor 73 is, for example, a CCD camera, a CMOScamera and the like. As a result, the worker or an administrator and thelike located at a place far from the work site can observe the state ofthe surface and a state inside the laser head and can obtain informationfor determining a degree of required coating removal or necessity ofmaintenance. The control unit 35 can collect information relating to thestate of the surface detected by such a sensor (hereinafter referred toas “surface-state information”). Moreover, the control unit 35 maycontrol such that this surface-state information is displayed on thedisplay apparatus of the operating unit 36. Alternatively, thissurface-state information may be notified to the display apparatus(reference numeral 82 in FIG. 14) connected to the laser head 3D mainbody wirelessly or by wire. Moreover, the surface-state information maybe transmitted to a server connected to this laser irradiation apparatuswirelessly or by wire. The control unit 35 may change the laserirradiation condition on the basis of the detected surface-stateinformation or may re-set the laser irradiation condition on the basisof an instruction inputted by the worker on the basis of thesurface-state information. Moreover, the laser irradiation conditionsuitable for the coating removal at the site is selected on the basis ofthe obtained surface-state information, and each setting of the laserirradiation apparatus including the laser head may be changed on thebasis of the selected laser irradiation condition.

Moreover, a sensor capable of detecting a toxic reaction gas may beprovided inside the attachment (not shown). The control unit 35 may beconfigured to issue an alarm to the worker and the administrator whenoccurrence of the toxic gas is detected.

The inter-surface distance measuring sensor 75 is a sensor for measuringa distance to the surface by infrared rays and the like. The controlunit 35 can set the focal point at a position suitable for the coatingremoval on the basis of the inter-surface distance detected by such asensor. Specifically, when the attachment 5 is in contact, theexpansion/contraction mechanism of the attachment 5 is controlled sothat the surface 20 to be treated is arranged at a distance equal to orcloser than the focal distance of the laser beam. Moreover, the variablefocusing mechanism of the optical system is controlled so that the focaldistance of the laser beam becomes equal to or longer than the measuredinter-surface distance.

Furthermore, as the inter-surface distance measuring means, anirradiation means (laser pointer or the like) using red laser may beused. FIG. 12 is an example of arrangement of the laser pointer in thelaser head, and FIG. 13 is an example of pointing of a focal point bythe laser pointer. In FIGS. 12 and 13, two laser pointers 77 areprovided in the laser head as the inter-surface distance measuring means(only one on the front is shown in FIG. 12). Each of the laser pointers77 is arranged so that its red laser beam 80 is irradiated diagonally tothe optical axis of the scanning optical system 4 and crosses the redlaser beam from the other laser pointer 77 at a predetermined distance(position) s. In FIG. 12, they are arranged so as to cross each other ata position S on the optical axis L of the scanning optical system 4 andare configured to be a guide of the inter-surface distance and so that acenter of the irradiation point of the laser beam can be grasped. Asdescribed above, by setting the distance s to a desired inter-surfacedistance, the irradiation position of the laser head can be grasped.Note that the red laser beams from the laser pointers 77 do not have tocross each other on the optical axis of the scanning optical system 4and may be arranged so as to cross each other at another position (apredetermined position on a front of the laser pointer 77, for example).Moreover, three or more laser pointers may be provided.

FIG. 13 illustrates a state in which the red laser beams 80 from the twolaser pointers are irradiated from two emitting ports 78 provided on atip-end cap of the laser head 3 and cross each other at the position S.By irradiating the red laser beams to the surface to be treated by suchtwo laser pointers, the worker can know an expected inter-surfacedistance from the principal point of the optical system to the surfacewhen moving the laser head longitudinally with respect the surface to betreated from the distance between the two light points of the laserpointers, and if the two light points match each other, for example, theworker can confirm that the laser head is at the appropriateinter-surface distance.

By referring to FIG. 11, the vibration detection sensor 74 is to detectvibration of the laser head 3D held by the worker and may be anacceleration sensor, for example. Moreover, this laser head 3D may beprovided with a vibrating means 76 for vibrating the laser head body.For the vibrating means, a vibration motor, a camera shake preventingmechanism mounted on a general camera and the like can be used. If thelaser beam 30 is continuously irradiated to a specific portion in acoating removal work, only the portion might be drilled deep. Thecontrol unit 35 preferably controls such that, if intensity of vibrationdetected by the vibration detection sensor 74 becomes smaller than apredetermined reference, the irradiation point P of the laser beam isvibrated finely by vibrating the laser head body 3D or the scanningoptical system 4 by using the vibrating means 76 so that the specificportion is not drilled too deep.

Moreover, the control unit 35 may notify the worker that the focal pointis at an appropriate position by the vibrating means 76 or the displayapparatus of the operating unit if it determines that the desiredposition of the focal point is obtained on the basis of measurement ofthe inter-surface distance by the inter-surface distance measurementsensor 75. Furthermore, the control unit 35 may stop irradiation of thelaser beam if it is determined that the focal point is not at a desiredposition on the basis of the measured inter-surface distance. If theattachment is mounted, the worker cannot usually check the irradiationpoint of the laser beam. The worker can check the optimal position byvibration or display, which is preferable.

Moreover, in this embodiment, it may be so configured that the fiberconnection portion 41 (laser emitting collimator) has a light collectingfunction. In general, the collimator has a function of convertingincident light to parallel light, and it may be so configured that thefocusing laser beam 30 can be emitted by incorporating a lightcollecting lens in this collimator. As a result, size and cost reductionof the laser head can be realized. Moreover, since the fiber connectionportion 41 (laser emitting collimator) is a final irradiation member ofthe fiber, heat can be easily accumulated. Thus, in order to preventoverheat of the fiber connection portion 41, a cooling means 38 may bearranged in the periphery. The cooling means 38 may be air-cooling orwater-cooling. For the cooling means 38, it may be so configured thatthe gas blowing means 34 disposed in the housing 32 is used to blow thegas press-fed from the gas supply source via the gas hose 12 to thefiber connection portion 41. Moreover, the gas blowing means 34 may beconfigured so that inflow of the removed matter generated from theirradiation point P into the housing and contamination of the opticalmember inside the housing and the scanning optical system 4 areprevented by filling the inside of the housing with a gas flow (purgegas). The gas blowing means 34 can be also used as the antistatic meansas described above, and by supplying the purge gas that can removestatic electricity (including ion, for example) to the inside of thelaser head so as to remove the charge from the removed matter chargedwith static electricity. Moreover, in this embodiment, instead of thegas blowing means 34 or in addition to the gas blowing means 34, ashielding member (not shown) for protecting the scanning optical systemfrom the removed matter generated from the laser irradiation point maybe provided.

The laser irradiation apparatus including the laser head having thevarious sensors of this embodiment may be connected to an externalserver via a network. The server can store various types of informationobtained by the various sensors, select conditions of laser irradiationon the basis of the various types of information and instruct an optimalcondition to the laser irradiation apparatus located at a remote site. Asystem provided with the laser irradiation apparatus will be explainedbelow.

Sixth Embodiment

FIG. 14 is an outline diagram illustrating an entire configuration of alaser irradiation system of a sixth embodiment. The laser irradiationsystem connects the laser irradiation apparatus arranged at a work siteand a server placed at a remote site to each other via a network, sets alaser irradiation condition on the basis of information of the coatingstate obtained by the laser irradiation apparatus and the like andrealizes an efficient coating work according to a state of the structuresurface.

This system is provided with the laser irradiation apparatus includingthe small-sized and light-weighted laser head 3 used at a work site anda server, and both are connected to each other via a network. In thelaser irradiation apparatus, the laser head 3 used at a work site isconnected to various apparatuses mounted on a vehicle 100 arranged inthe vicinity of the work site via the integrated cable 25 (including thefiber 2, the suction hose 8, the gas hose 12, and a power cable). Thevehicle 100 is preferably a runnable vehicle but in addition, a boat, abarge, a carriage configured to be movable via a rail or a cable, and aplatform capable of autonomous running by a remote control may be used.On the vehicle 100, the laser oscillator 1, the suction source 9, andthe gas supply source 11 are mounted similarly to FIG. 1 and inaddition, a management terminal 82, a power supply apparatus 83 and thelike are mounted.

The management terminal 82 is a terminal for controlling the laserirradiation apparatus and has a function of creating informationrelating to a state of a surface (surface-state information) byobtaining information from the various sensors mounted on the laser head3, a function of creating information relating to maintenance managementof the laser irradiation apparatus (hereinafter referred to as“apparatus management information”), a function of managing the laserirradiation condition, a function of displaying various types ofinformation, a function of communicating with a server 84 via thenetwork and the like. For the management terminal 82, the control unitof the laser head 3, a personal computer and the like can be employed,for example. The power supply apparatus 83 supplies power to each of theapparatuses in the vehicle and the laser head 3.

The server 84 is a server managing a plurality of the laser irradiationapparatuses and has a function of storing various types of informationobtained from the management terminal 82 via a network 90, a function ofsetting the laser irradiation condition for efficient coating removalaccording to the work site or the surface of the target on the basis ofthe surface-state information and the like, a function of transmittingsuch irradiation conditions to each of the laser irradiation apparatusesvia the network 90, a function of maintaining/managing each of the laserirradiation apparatuses on the basis of the apparatus managementinformation, and the like.

Moreover, this system may be provided with a management terminal 85. Themanagement terminal 85 is a terminal for managing the server 84, and apersonal computer or the like can be employed, for example. Themanagement terminal 85 may be directly connected to the server 84 or maybe connected to the server 84 and the management terminal 82 via thenetwork. Administrators can access the server 84 and the managementterminal 82 of the laser irradiation apparatus via the managementterminal 85.

It is only necessary that the network 90 allows the management terminal82 of the laser irradiation apparatus (or a communication apparatus, notshown) and the server 84 to be communicable with each other. Forexample, a public telephone network, ISDN (Integrated Service DigitalNetwork. Also referred to as Digital Integrated Service Network), ADSL(Asymmetric Digital Subscriber Line), CATV (Community AntennaTeleVision) network, an optical fiber network, a wireless LAN (LocalArea Network), CS (Communication Satellite) broadcasting, a mobile phonenetwork and the like can be used.

The apparatus management information includes, for example,identification information, model, use situation (use time and date,cumulative use time, use frequency, use condition, component replacementhistory) of the laser head 3 and the like. The surface-state informationincludes information relating to the state of the coating (thickness ofthe coating, an area of an active film, a state of rust and stain,closeness (moisture)), quality of a base material (undercoat), a shapeof the target surface (plane, a corner part, a protrusion), and a typeof a structure (a bridge, a tank and the like). Moreover, suchsurface-state information may be associated to the laser irradiationcondition when the surface is actually subjected to coating removal (alaser output, a laser wavelength, a focal distance, a defocusing amount,a spot diameter, a mode of scanning (a rotation speed, a scanningspeed), energy density, a removed amount and the like), informationrelating to the surface of the structure after the laser irradiation,and a weather condition (a temperature, humidity and the like).

The server 84 of this system can select the appropriate laserirradiation condition according to the state of the surface of each worksite on the basis of the obtained surface-state information and/or pastachievements of the laser irradiation and transmit the selected laserirradiation condition to each of the laser irradiation apparatuses.Moreover, the server 84 may have a function of creating a database byassociating the surface-state information with the laser irradiationcondition. Moreover, the server 84 may be configured to transmit asignal for allowing or prohibiting irradiation of the laser beam to thelaser irradiation apparatus on the basis of information from the sensorgroup (contact of the attachment, the inter-surface distance, thesurface state and the like). Furthermore, the server 84 may notify ormanage timing and contents of the maintenance on the basis of theapparatus management information obtained from each of the laserapparatuses.

As a method in which the laser irradiation apparatus obtains a laserirradiation condition from the server 84, a configuration usingoperation on the laser irradiation apparatus-side as a trigger may beemployed, or the laser irradiation condition may be provided to thelaser irradiation apparatus from the server 84 independently from theoperation on the laser irradiation apparatus-side. Specifically, ifthere is operation on the laser irradiation apparatus-side such astransmission of the surface-state information, a condition deliveryrequest inputted from the worker, power-on of the laser head and thelike, the server 84 obtains the surface-state information and selects anappropriate laser irradiation condition on the basis of such surface-state information and transmits the selected condition to the laserirradiation apparatus at the work site. Moreover, the server 84 mayobtain various types of information stored in the management terminal 82of the laser irradiation apparatus independently from the operation onthe laser irradiation apparatus-side on the basis of the identificationinformation registered in advance and the like, select the appropriatelaser irradiation condition on the basis of them and store the selectedcondition in the management terminal 82 of the laser irradiationapparatus. Note that, in the above-described explanation, the case inwhich the server 84 transmits the laser irradiation condition isexplained, but a configuration in which the management terminal 82 ofthe laser irradiation apparatus obtains the laser irradiation conditionstored in the server 84 may be employed.

The management terminal 82 (or the control unit 35) may automaticallymake setting of the irradiation apparatus on the basis of the obtainedlaser irradiation condition. Moreover, it may display the obtained laserirradiation condition on a display portion of the management terminal 82or the operating unit 36 of the laser head 3, for example. Moreover, itmay be so configured that the worker can adjust various settingsmanually and the laser irradiation condition can be changed asappropriate in accordance with a change in the situation of the site.Note that, from the viewpoint of safety management, an adjustable range(a maximum value of an output and the like) is preferably limited.

Moreover, the administrator may determine a grade of coating removal andnotify the grade to the worker of the work site on the basis of thesurface-state information and a result of visual observation by acamera. In re-painting of a structure, a required grade of coatingremoval is classified to Class 1 scraping to Class 4 scraping. Forexample, in the Class 1 scraping, a coating, rusts and the like on thesurface are fully removed, and a surface of iron of metallic luster isfully exposed. In the Class 2 scraping, a firmly adhering coating isremoved, and other coatings, corrosive substances, fat and oil, stainsand other foreign substances are removed. In the Class 3 scraping, rustsand floating coatings are removed, while an active film is left. In re-painting of the structure, the Class 2 scraping and the Class 3 scrapingare generally used, but the Class 1 scraping is employed in many casesfor structures with remarkable coating deterioration of a steel materialin recent years.

As described above, according to this embodiment, the server can selectand instruct a laser irradiation condition suitable for coating removalto the laser irradiation apparatus on the basis of information detectedby the various sensors mounted on the laser head.

Seventh Embodiment

In this embodiment, another example of the circular scanning of thelaser beam is explained, which is a mode in which the focusing laserbeam is deflected so as to have a circular trajectory and then,deflected again in the optical axis direction in order to irradiate sothat the optical path of the laser beam crosses at the optical axis.

FIG. 15 is an outline configuration diagram illustrating an example of alaser head of a seventh embodiment. This laser head 3E is different fromthe laser head 3B of the third embodiment illustrated in FIG. 5 in apoint that the first wedge prism 43 and the second wedge prism 45 arefixed and provided on the support member 44 so that a rotationdifference is not generated in each prism and in a point in which adome-shaped shielding member 48 having the laser emitting port 50 on theoptical axis is provided. In the laser head 3E of the seventhembodiment, the same configurations as those in the laser head 3B of thethird embodiment are given the same reference numerals and detailedexplanation will be omitted.

In this example, the first wedge prism 43 and the second wedge prism 45are supported by the support member 44, and the first wedge prism 43 andthe second wedge prism 45 are rotated around the optical axis together(at the same rotation speed) by driving force from the driving means 49.

The first wedge prism 43 deflects the optical path of the laser beamwith respect to the optical axis L by the deflection angle θ1 in thedirection outward from the rotation center (optical axis L).Subsequently, the second wedge prism 45 deflects the optical path of thelaser beam with respect to the deflected optical path M by thedeflection angle θ2 in the direction toward the rotation center (opticalaxis L) (wherein 02>01). In this example, since the laser beam havingbeen deflected outward with respect to the optical axis L once isdeflected again inward, the laser beams apparently cross at anintersection X in accordance with motions of the two prisms rotatingintegrally. In other words, this example is a configuration in which thelaser beam 30 is irradiated from the intersection X with an angle(θ2−θ1) from the optical axis L.

As described above, in this example, since the emitting port 50 of theshielding member 48 is arranged in correspondence with a position of theintersection X of the laser beam, the emitting port in the shieldingmember 48 can be set small on the optical axis, and entry of the removedmatter generated from the irradiation point of the laser beam on thetreatment plane into the laser head can be prevented while the laserbeam is irradiated circularly. Note that, in this example, a third wedgeprism may be provided on the positive side (on the side of the surfaceto be treated in the figure), and the third wedge prism may be rotatedat a rotation speed different from those of the first and second wedgeprisms. In this case, the mode of the circular scanning as illustratedin FIG. 5 can be realized. Note that, though this embodiment is notconfigured to collect the removed matter generated from the laserirradiation point P, if the removed matter is not to be scattered to theperiphery, an attachment and a suctioning means may be further provided.

FIG. 16 is an outline configuration diagram illustrating another exampleof the laser head of the seventh embodiment. The laser head 3F of thisexample is provided with the suctioning means 31 having the attachment 5and the suction port 33 as an additional configuration to the laser head3E illustrated in FIG. 15. According to the laser head of this example,the optical system of the laser head can be protected from the removedmatter generated from the irradiation point of the laser beam and theremoved matter can be collected without scattering to the periphery.

Eighth Embodiment

In an aspect of the present invention, a variation when an adheringmatter inside a pipeline is to be removed will be explained. In thisexample, the laser beam is not irradiated circularly to a plane surfaceto be treated but the laser beam is irradiated circularly in accordancewith an inner diameter of the inside of the pipeline. This example isparticularly suitable for an application for removing an adhering mattercontaining a radioactive substance inside a secondary cooling pipelineof a nuclear reactor.

FIG. 17 is an outline configuration diagram illustrating an example of alaser head of an eighth embodiment. A laser head 3G of this exampleincludes the wedge prism 43, the support member 44, the driving means49, the fiber connection portion 41, the suctioning means 31 having thesuction port 33, and a moving means 110. Since this laser head 3G isused by being inserted into a pipeline with a small diameter, it ispreferably made as small as possible, and the fiber connection portion41 can preferably supply the laser beam with high energy as it is fromthe emitting end without using a focusing means.

Main bodies (41, 43, 44, 49) of the laser head 3G are placed on a movingmeans 110A capable of running automatically or manually inside apipeline 20, and the suctioning means 31 is placed on a moving means110B arranged in a traveling direction of the laser head body. Each ofthe moving means 110A and 110B can have a roller 112 for traveling andan appropriate driving means (not shown) and move along the inside ofthe pipeline, for example. The moving means 110A and 110B are preferablyconfigured to be movable by remote control.

Moreover, in the moving means 110A and 110B, a sealing means 114 capableof close contact with the surface of the inside of the pipeline ispreferably provided. The sealing means is constituted by rubber or resinpacking, brush or the like. As a result, since a space between themoving means 110A and the moving means 110B is closed, scattering ofharmful removed matters and the like removed by the laser irradiationcan be prevented.

The laser head 3G irradiates the laser beam 30 circularly in accordancewith an inner diameter of the pipeline 20 while traveling in thepipeline by the moving means 110A. That is, since the irradiation pointP of the laser beam is scanned so as to draw a trajectory of a circlehaving a radius r corresponding to ½ of the inner diameter of thepipeline, the adhering matter 22 inside the pipeline can be efficientlyremoved. The moving means 110B on which the suctioning means 31 isplaced travels together with the moving means 110A on which the laserhead body is placed, and the removed matter 60 generated from theirradiation point of the laser beam 30 is collected by the suctioningmeans 31.

FIG. 18 is an outline configuration diagram illustrating another exampleof the laser head of the eighth embodiment. The laser head 3H of thisexample is different from the example illustrated in FIG. 17 in a pointthat a reflective mirror 43B is used instead of the wedge prism, and thesuctioning means 31 is provided on the main body side of the laser head.The reflective mirror 43B is provided on the tip-end of the laser headand rotated by the driving means 49. In this laser head 3H, the laserbeam 30 emitted from the fiber connection portion (laser emittingcollimator) 41 is reflected by the predetermined angle θ by the rotatingreflective mirror 43B. The reflected laser beam 30 goes to the rear ofthe tip-end of the laser head. The irradiation point P of the laser beamis scanned so as to draw the trajectory of the circle having the radiusr corresponding to ½ of the inner diameter of the pipeline, and thus,the adhering matter 22 inside the pipeline can be efficiently removed.The removed matter 60 generated from the irradiation point of the laserbeam 30 is collected by the suctioning means 31 placed on the movingmeans 110.

According to this example, the laser head can travel inside the pipelineand scan the irradiation point of the laser beam circularly conformingto the inner diameter of the pipeline and thus, removal of the adheringmatter inside the pipeline which has been difficult can be performedefficiently and safely.

Note that FIG. 17 illustrates the configuration in which one wedge prismis used as the scanning optical system and FIG. 18 illustrates theconfiguration in which one reflective mirror is used as the scanningoptical system, but the laser head of the eighth embodiment is notlimited to those configurations. The configurations of the otherembodiments (FIGS. 1, 3, 5, 8, 15, 16 and the like, for example) may becombined with the laser head in FIG. 17 or FIG. 18.

Ninth Embodiment

In this embodiment, a laser head including a replaceable optical unitwill be explained. FIG. 19(A) is an outline configuration diagram of thescanning optical system (when connected) including the replaceableoptical unit in a laser head of a ninth embodiment, and FIG. 19(B) is anoutline configuration diagram when the replaceable optical unit isremoved (when separated). The scanning optical system of the laser headof this embodiment is constituted by connecting a replaceable opticalunit 190 including an optical member at least for focusing or deflectingand a body portion 191 including at least the driving means 49 (see FIG.19(A)), and the replaceable optical unit 190 is configured to bedetachably attached to the body portion 191 of the laser head withsimple operation (see FIG. 19(B)), and an irradiation condition of thelaser beam can be easily changed.

The replaceable optical unit 190 is a unit including various opticalmembers (one or more of a wedge prism, a light collecting lens, areflective mirror and the like, for example) and at least a part of or awhole of the replaceable optical unit 190 is made rotatable by drivingforce applied by the driving means 49. In FIG. 19, it is constituted bythe support member 44 rotatably holding a lens holder body 44A, a lenscap 44B, a joint cap 44C and the like. The lens holder body 44A storesvarious optical members therein and is closed by the lens cap 44B on thefront and by the joint cap 44C on the rear. It is only necessary thatthe optical members requiring conditional changes are arranged in thereplaceable optical unit, while the other optical members may bearranged in the body portion 191. The lens cap 44B has an openingthrough which the laser beam passes. The joint cap 44C has an openingthrough which the laser beam passes provided and has a structure engagedwith a connecting member 49B of the body portion 191 so that a rotatingforce of the driving means can be transmitted. Thus, at least a part ofthe replaceable optical unit 190 can be rotated by the driving forceapplied by the driving means 49 but can be separated from the bodyportion 191 including the driving means 49 by simple operation and canbe removed from the laser head.

Moreover, on a tip-end of the replaceable optical unit 190, the laseremitting port 50 for emitting the laser beam is provided. The laser beamemitted from the replaceable optical unit 190 is circularly scanned bythe various optical members stored in the lens holder body 44A, forexample, and emitted toward the surface to be treated from the laseremitting port 50. Moreover, in order to prevent entry of the removedmatter into the optical unit 190, the gas supplied form the gas supplysource (not shown) may be injected from the laser emitting port 50. Notethat a gas blow-out port 34B may be provided instead of the laseremitting port 50 or in addition to the laser emitting port 50 in theperiphery of the laser emitting port 50 so that the gas supplied fromthe gas supply source (not shown) is injected. Moreover, in thereplaceable optical unit 190, a laser pointer (reference numeral 77illustrated in FIG. 12) may be arranged, and a hole of the laser pointer(reference numeral 78 illustrated in FIG. 12) may be provided. The bodyportion 191 is constituted by a hollow motor 49A which is the drivingmeans 49, the connecting member 49B and the like.

As a method for connecting the replaceable optical unit 190 to the bodyportion 191, the joint cap 44C of the replaceable optical unit 190 andthe connecting member 49B of the body portion 191 may be fixed via ahook or the like, for example, so that the driving force by the drivingmeans 49 is transmitted to the replaceable optical unit 190 via theconnecting member 49B and the joint cap 44C.

Moreover, the replaceable optical unit 190 may be connected to the bodyportion 191 by fixing the support member 44 to the housing 32 of thebody portion 191 in a state in which the joint cap 44C and theconnecting member 49B are engaged capable of transmitting a rotarymotion. In this case, in the state in which the support member 44 isfixed to the housing 32 of the body portion 191, the lens holder body44A may be configured to make a rotary motion inside the support member44 via a sliding means such as a bearing. Note that, it is preferablethat the additional configuration (such as a laser pointer and the like)is attached to the replaceable optical unit 190 in advance before thereplaceable optical unit 190 is connected to the body portion 191.

As described above, in this embodiment, since the replaceable opticalunit is employed, by selecting and attaching an appropriate unitaccording to a purpose (a type, a state, a size and the like of a matterto be treated), various irradiation modes of the laser beam can berealized. Specifically, by selecting a unit including a single wedgeprism, the circular scanning as illustrated in FIG. 4 can be realized.By selecting a unit including two wedge prisms (with a rotation speeddifference), the annular scanning as illustrated in FIG. 6 or FIG. 7 canbe realized. By selecting a unit including two wedge prisms (no rotationspeed difference), the circular scanning illustrated in FIG. 15 can berealized.

Furthermore, by selecting an appropriate unit in a plurality of unitsincluding wedge prisms with deflection angles different in steps, thecircular scanning with a desired radius r according to a purpose can berealized. Moreover, various irradiation conditions may be changed byproviding in the scanning optical system a focal distance of adeflection angle capable to be changed. For example, by changing thereplaceable optical unit as appropriate to change the deflection angle,the size of the circular scanning (diameters 10 cm, 5 cm, 3 cm and thelike, for example) can be changed with substantially the sameinter-surface distance, and by changing the focal distance, the desiredinter-surface distance is changed, and as a result, the size of thecircular scanning (diameters 10 cm, 5 cm, 3 cm and the like, forexample) can be also changed. Regarding the size of the circularscanning (diameters 10 cm, 5 cm, 3 cm and the like, for example),large-sized circular scanning may be used for a large area, whilesmall-sized circular scanning may be used for a small area such as anarrow part in accordance with an area of the surface to be treated.

Moreover, when the laser beam with the same energy is to be irradiated,if the size of the circular scanning is changed, energy density at theirradiation position is also changed. Thus, the size of the circularscanning may be changed by selecting the replaceable optical unit inaccordance with the desired energy density to be applied to the surfaceto be treated. Moreover, the energy density of the laser irradiation tobe applied to the surface to be treated can be adjusted by changing thesize of the circular scanning in accordance with a specified output ofthe laser oscillator to be used, and there is less concern thatexcessive energy is applied. Furthermore, the replaceable optical unitmay be selected in accordance with the state of the surface to betreated, and if the Class 3 scraping for removing rusts on a surfacelayer or floating coating is to be performed, for example, thereplaceable optical unit capable of large-sized circular scanning can beselected so that the energy density of the laser irradiation is madesmaller. By using the replaceable optical unit as above, maintenance andservice of the optical member is facilitated. Note that, to the laserhead including the replaceable optical unit of this embodiment, too, thevarious attachments (reference numeral 5 illustrated in FIG. 1 or FIG.11, reference character 5B illustrated in FIG. 8, reference character 5Cillustrated in FIG. 10 and the like) can be attached.

EXAMPLE 1

As an example of the present invention, a laser head was designed asfollows. The laser head had a length of 43 cm, a diameter of 7 cm, and aweight of 1400 g. In the laser head having the first and second wedgeprisms, a focal distance was set to 150 mm and a beam spot diameter at afocal point to 0.04 mm (40 μm). The laser beam entering the laser headis of a continuous oscillation type having an average output of 200 Wand a wavelength of 1070 nm. The laser head attached with an attachmentwas brought into contact with a flat-plane shaped steel plate on which acoating with a thickness of 30 to 50 μm was formed, and the laser beamwas irradiated to a surface of the steel plate substantiallyperpendicularly. By using such laser head, treatment of coating removalwith work efficiency of 8 m² per hour was possible.

EXAMPLE 2

Moreover, as another example of the present invention, a laser head forwhich the replaceable optical unit was employed was designed. FIGS. 20are appearance views of the example of the laser head for which thereplaceable optical unit was employed. FIGS. 20(A), 20(B), 20(C), and20(D) are a side view, a top view, a perspective view when seen from atip-end side, and a perspective view when seen from a rear end side ofsuch laser head, respectively. This laser head had a length of 35 cm, aheight of 8.5 cm, a width of 6 cm, and a weight of 1.6 kg. Thereplaceable optical unit 190 included a light collecting lens, a wedgeplate, and a protective glass (a part of a shielding member), wasdetachably attached to the body portion 191, and was connected so that adriving force can be transmitted via the driving means and theconnecting member of the body portion 191.

By referring also to FIG. 19, the joint cap 44C of the replaceableoptical unit 190 was connected to the connecting member 49B of the bodyportion 191, capable of transmitting a rotary motion, and a housing 44itself on the outside of the replaceable optical unit 190 was fixed tothe housing 32 of the body portion 191. The lens holder body 44A storingthe optical member inside the replaceable optical unit 190 wasconfigured so as to rotate along the inner side of the housing 44 of thereplaceable optical unit 190 via a bearing. When the replaceable opticalunit 190 is to be mounted to the body portion 191, the joint cap 44C isengaged with the connecting member 49B, and the replaceable optical unit190 is inserted while being rotated in one direction. When thereplaceable optical unit 190 is to be removed from the body portion 191,the replaceable optical unit 190 is pulled out while being rotated in adirection opposite to that in mounting. The replaceable optical unit 190has a length of 4 cm, a height of 8.5 cm, and a width of 6 cm and if onewedge prism is included, the weight is 200 to 300 g.

As described above, according to each of the embodiments of the presentinvention, by scanning the laser irradiation point on the surface of thestructure, a coating can be removed efficiently in a short time.Moreover, since the position of a focal point can be set as appropriateby the expansion/contraction mechanism of the attachment and the like,irradiation energy, a spot diameter and the like can be selectedaccording to the state of the surface. According to the presentinvention, unlike the conventional blast treatment, since physicalcontact with the surface is not involved and a quiet laser is used, aninfluence of a noise to the ambient environment is small. Moreover,according to an aspect of the present invention, by employing thevarious attachments, a coating and an adhering matter at a complicatedspot, a periphery of a protrusion, a narrow part, on an inside of apipeline and the like where treatment has been difficult with theconventional method can be removed.

Note that the first to ninth embodiments have been explained, but theapplication range of the present invention is not limited by therespective embodiments. For example, a plurality of the embodiments maybe combined or a part of the configuration of each of the embodiments(configurations of the attachment, the shielding member, the suctioningmeans, the scanning optical system, the laser pointer and itsirradiation hole, the supply port of the gas supply means and the like)can be combined with each other.

[Reference Numerals]

-   1 laser oscillator-   2 fiber-   3 laser head-   4 scanning optical system-   5 attachment-   7 sensor group-   9 suction source-   11 gas supply source-   20 surface-   30 laser beam-   31 suction means-   32 housing-   33 suction port-   34 gas blow-out port-   35 control unit-   36 operating unit-   48 shielding member-   100 vehicle

1-49. (canceled)
 50. A coating removing method for removing a coating ofa surface of a structure by laser irradiation from a laser irradiationapparatus for focusing a laser beam outputted from a laser oscillatorand irradiating it to the surface of the structure, characterized inthat: the laser irradiation apparatus performs scanning so that airradiation point of a focused laser beam rotates on the surface of thestructure, while the laser irradiation apparatus is moved with respectto the structure to keep a distance between the laser irradiationapparatus and the surface of the structure to be treated substantiallyconstant.
 51. The coating removing method according to claim 50,characterized in that: the laser irradiation apparatus performs a rotaryscanning so that the irradiation point of the focused laser beam draws atrajectory of a substantially circle having a substantially constantradius on the surface of the structure.
 52. The coating removing methodaccording to claim 50, characterized in that: the laser irradiationapparatus has a deflecting means for deflecting the laser beam withrespect to the optical axis of the focused laser beam at a predeterminedangle; and the deflecting means rotates the focused laser beam aroundthe optical axis so as to rotate the irradiation point of the focusedlaser beam on the surface of the structure.
 53. The coating removingmethod according to claim 50, characterized by moving the laserirradiation apparatus with respect to the structure so that theirradiation point of the laser beam on the surface of the structuredraws a trajectory of a substantially circle having a radius within arange of 5 to 200 mm.
 54. The coating removing method according to claim50, characterized in that: the laser irradiation apparatus has a laserhead, and the laser head is provided with: the laser oscillator; anoptical system for focusing the laser beam outputted from the laseroscillator and irradiating it to the surface of the structure; ashielding member for protecting the optical system from a removed mattergenerated from the surface of the structure; and an emitting portprovided in the shielding member and open to an optical path of thelaser beam irradiated on the surface of the structure.
 55. The coatingremoving method according to claim 50, characterized in that the laserirradiation apparatus is moved linearly with respect to the surface ofthe structure so as to remove a coating of the surface of the structure.56. The coating removing method according to claim 50, characterized inthat the surface of the structure is kept within a range of 5 to 25 mmcloser to the laser irradiation apparatus side than the focal positionof the laser beam.
 57. A coating removing method for removing a coatingof a surface of a structure by laser irradiation from a laserirradiation apparatus for focusing a laser beam outputted from a laseroscillator and irradiating it to the surface of the structure,characterized in that: the laser irradiation apparatus has an opticalsystem comprising a first deflecting means for deflecting the laser beamwith respect to an optical axis of the focused laser beam at apredetermined angle and a second deflecting means for deflecting thefocused laser beam deflected by the first deflecting means at apredetermined angle; the irradiation point of the focused laser beamthrough the second deflecting means is subjected to rotary scanning soas to draw a trajectory of a substantially circle having a constantradius r2 around a circumference of a substantially circle having aconstant radius r1 on the surface of the structure; and the laserirradiation apparatus is moved with respect to the structure to keep adistance between the laser irradiation apparatus and the surface of thestructure to be treated substantially constant.
 58. The coating removingmethod according to claim 57, characterized in that: the laserirradiation apparatus has a laser head, and he laser head is providedwith: the laser oscillator; an optical system for focusing the laserbeam outputted from the laser oscillator and irradiating it to thesurface of the structure; a shielding member for protecting the opticalsystem from a removed matter generated from the surface of thestructure; and an emitting port provided in the shielding member andopen to an optical path of the laser beam irradiated on the surface ofthe structure.
 59. The coating removing method according to claim 57,characterized in that the laser irradiation apparatus is moved linearlywith respect to the surface of the structure so as to remove a coatingof the surface of the structure.
 60. The coating removing methodaccording to claim 57, characterized in that the surface of thestructure is kept within a range of 5 to 25 mm closer to the laserirradiation apparatus side than the focal position of the laser beam.61. A coating removing apparatus for removing a coating of a surface ofa structure by laser irradiation from a laser irradiation apparatus forfocusing a laser beam outputted from a laser oscillator and irradiatingit to the surface of the structure, characterized in that: the laserirradiation apparatus performs scanning so that a irradiation point of afocused laser beam rotates on the surface of the structure, while thelaser irradiation apparatus is moved with respect to the structure tokeep a distance between the laser irradiation apparatus and the surfaceof the structure to be treated substantially constant.
 62. The coatingremoving apparatus according to claim 61, characterized in that: thelaser irradiation apparatus includes an optical system for performing arotary scanning so that the irradiation point of the focused laser beamdraws a trajectory of a substantially circle having a substantiallyconstant radius on the surface of the structure.
 63. The coatingremoving apparatus according to claim 61, characterized in that: theoptical system has a deflecting means for deflecting the laser beam withrespect to the optical axis of the focused laser beam at a predeterminedangle; and the deflecting means rotates the focused laser beam aroundthe optical axis so as to rotate the irradiation point of the focusedlaser beam on the surface of the structure.
 64. The coating removingapparatus according to claim 61, characterized by moving the laserirradiation apparatus with respect to the structure so that theirradiation point of the laser beam on the surface of the structuredraws a trajectory of a substantially circle having a radius within arange of 5 to 200 mm.
 65. The coating removing apparatus according toclaim 61, characterized in that: the laser irradiation apparatus has alaser head, and the laser head is provided with: the laser oscillator;an optical system for focusing the laser beam outputted from the laseroscillator and irradiating it to the surface of the structure; ashielding member for protecting the optical system from a removed mattergenerated from the surface of the structure; and an emitting portprovided in the shielding member and open to an optical path of thelaser beam irradiated on the surface of the structure.
 66. The coatingremoving apparatus according to claim 65, characterized in that thelaser head includes an attachment for abutting on the surface of thestructure and keeping a distance between the laser head and the surfaceof the structure to be treated substantially constant.
 67. The coatingremoving apparatus according to claim 66, characterized in that theattachment has an inner wall on the surface side of the structure so asto reflect the laser beam irradiated from the laser head to the surfaceside of the structure.
 68. The coating removing apparatus according toclaim 61, characterized in that the laser irradiation apparatus is movedlinearly with respect to the surface of the structure so as to remove acoating of the surface of the structure.
 69. The coating removingapparatus according to claim 61, characterized in that: the laserirradiation apparatus has a laser head; and the laser head includes: alaser head body for accommodating the laser oscillator and a drivingmeans for rotatively driving the optical system; and a replaceableoptical unit capable of connecting to the laser head body, accommodatingat least a part of the optical system, and having an emitting port ofthe laser beam irradiated from the optical system.
 70. A coatingremoving apparatus for removing a coating of a surface of a structure bylaser irradiation from a laser irradiation apparatus for focusing alaser beam outputted from a laser oscillator and irradiating it to thesurface of the structure, characterized in that: the laser irradiationapparatus has an optical system comprising a first deflecting means fordeflecting the laser beam with respect to an optical axis of the focusedlaser beam at a predetermined angle and a second deflecting means fordeflecting the focused laser beam deflected by the first deflectingmeans at a predetermined angle; the irradiation point of the focusedlaser beam through the second deflecting means is subjected to rotaryscanning so as to draw a trajectory of a substantially circle having aconstant radius r2 around a circumference of a substantially circlehaving a constant radius r1 on the surface of the structure; and thelaser irradiation apparatus is moved with respect to the structure tokeep a distance between the laser irradiation apparatus and the surfaceof the structure to be treated substantially constant.
 71. The coatingremoving apparatus according to claim 70, characterized in that: thelaser irradiation apparatus has a laser head, and the laser head isprovided with: the laser oscillator; an optical system for focusing thelaser beam outputted from the laser oscillator and irradiating it to thesurface of the structure; a shielding member for protecting the opticalsystem from a removed matter generated from the surface of thestructure; and an emitting port provided in the shielding member andopen to an optical path of the laser beam irradiated on the surface ofthe structure.
 72. The coating removing apparatus according to claim 71,characterized in that the laser head includes an attachment for abuttingon the surface of the structure and keeping a distance between the laserhead and the surface of the structure to be treated substantiallyconstant.
 73. The coating removing apparatus according to claim 72,characterized in that the attachment has an inner wall on the surfaceside of the structure so as to reflect the laser beam irradiated fromthe laser head to the surface side of the structure.
 74. The coatingremoving apparatus according to claim 70, characterized in that thelaser irradiation apparatus is moved linearly with respect to thesurface of the structure so as to remove a coating of the surface of thestructure.
 75. The coating removing apparatus according to claim 70,characterized in that: the laser irradiation apparatus has a laser head;and the laser head includes: a laser head body for accommodating thelaser oscillator and a driving means for rotatively driving the opticalsystem; and a replaceable optical unit capable of connecting to thelaser head body, accommodating at least a part of the optical system,and having an emitting port of the laser beam irradiated from theoptical system.